The meat of my question is, will a JK dana 30 shaft fit into a Xj dana 30 carrier?

For context I had planned on pairing a Crown Victoria 8.8 (66 in WMS to WMS) with a JKU Dana 4 front Axle (66 in WMS to WMS) and run 35s with light skinny pedal use. Things have changed and I am now walking that goal back to just the 8.8 I already have installed, as there's no way I'm keeping a Dana 35 or anything else without disks on the rear. I do not want my rear tires sticking out 3 inches extra each side in the rear and am looking for solutions to this. I am not going to run front wheel spacers bigger than 1.5 inches or super low offset front wheels as I like my ball joints to work. I have found it to be impossible to find any 15 x 8 steel wheels that have between 5.5 and 6.5 in backspacing that fit or this problem would be solved.

So this leaves my next cheapest option that I can think of being hopefully widening the front axle. I know I will be upgrading brakes and steering so doing some fab work to make that happen is not a issue. Will the JK dana 30 shafts fit into everything else fine if I throw in the extra tube to the axle to make the width match? Will I need JK knuckles and steering?

Why not just put mounts on a JK axle and stuff it under the XJ, seems like a lot less work.

WJ D30 is 65" WMS

Physically, yes, the JK shaft will slide into the XJ carrier, but that seems like a fool's errand. Definitely just get a WJ Dana 30 or JK axle and be done with it. I have a JK Dana 44 I'm planning on swapping into the front.

I can't speak to the WJ axle, but the JK axle has a low pinion/caster separation. Most people cut/turn the C's when they swap them into other vehicles. Also, both of those vehicles have a 5x5 bolt pattern. The WJ setup has superior steering geometry and brakes.

To my knowledge the Dana 30s are low pinion or I would do so.

Getting a WJ or JK axle under the XJ seems to be a similar amount of work to me for a inferior end result.

I knew the WJ Dana was a little wider but I didn't know it was that wide, I now have my mind on just chopping the ends of a WJ and solving my steering, brakes, and width in one go. I have a JK sleeve kit on hand so keeping everything straight should be a little easier if I chop that to WJ length but it in the XJ and throw the ends of the WJ axle on. I know I will have to be cautious of bending the axle and will prep it as if I am putting on a truss. I will also be wary of HAZ and add more reinforcement to the ends of the axle especially since they will now be under more stress due to more leverage.

Am I missing anything?

Simply sticking shafts into it won't widen it and widening an XJ 30 housing will be more work than putting JK axle under it. A lot of jk swap brackets on the market

You are making it way too complicated. If you are staying with 35s a HP Dana 30 and Chrysler 8.25 can handle that.

I feel that the extra work to get where I want would consist of going to the junkyard finding a WJ and taking out the shafts, cutting the housing off at the ends with a little extra room to get everything measured properly back home. Taking off the C's knuckles brakes steering ect that I want anyway with it. From there if I measure my Dana 30 sleeves I have I can cut them to the right length put them in the existing Dana 30 with the stock housing cut and slide the new ends from the WJ on when they are at the right length. From there I would only have one weld each side which I don't thing would be much harder to keep straight than doing a JK swap bracket.

From what I can tell I'd be saving about 600$ having a better axle (compared to LP) not have to grab another person to help me take a axle home, not have to worry about warping the housing as much, and have to do less welding overall if I widen my Dana 30 compared to swiping one in.

I have a 8.8 already because I was thinking I'd be on 35's which Dana 30+8.25 are iffy on in terms of breakage, being too skinny to not worry about rolling, and not having good braking. It's staying on 33's and if I knew this I'd have considered the 8.25 as the diff ground clearance of the 8.8 on 33's = that of 8.25 on 31's.

I already think I know what I want which is a widened HP 30, my only other option I am considering is finding some wheels 15 x 6 or something like that and having them widened, which is done from the inside. Unless someone has knowledge of any steel or not supper expensive 15 x 8 that has between 5 and 7 inches of backspacing which would be a lifesaver but I've spent hours calling around and on the internet already.

An 8.8 out of a Crown vic is a 28 spline and not stronger than a 29 spline Chrysler 8.25, a 31 spline 8.8 out of an Explorer would be a better axle and is almost the same width as the front Dana 30. For 35s a Dana 30 holds up fine, been running 35s on my Dana 30 locked for almost 4 years and never had a problem.

An 8.8 out of a crown vic is not 28 spline. Unless for some reason you grab one out of a mid year 05 and previous. I got a Crown Vic rear because I wanted better housing strength without having to truss, wanted discs, more width, and about 150$ less on price from junkyard compared to SUV/trucks although that was kind of a bonus. I am not regretful of the purchase and understand that if I wanted to never spin tires or go full send and accept I'll break things a 8.25 would actually be better because of ground clearance. I want something that will make it home and would have likely ended on a 8.8 anyway.

All im gonna say is share plenty of pictures of the process.

Just my opinion but chopping the tubes off your XJ D30 to then butt weld the outers from a WJ D30 and then sleeve inside there just to gain a few inches in WMS is an incredible waste of time and effort. This sounds like a daydreamers paradise in theory sure things would line up but the loss in strength wouldn't sell it for me. JK 30's and 44's are prone to bending as it is for their width and tube size let alone a butted seam towards the outside of the axle - sleeved or not.