Changing oil pan, should I change oil pump while I have it opened up, and if so should I go with the high volume pump? Engine has 135,000 miles.

 

If you're asking my opinion, unless you have low oil pressure, I wouldn't bother. My 2000 has 213K miles on it with the original pump, 40psi pressure at idle hot, and 55 at 65 mph. A high volume pump will compensate for worn bearings, but throws more oil around in the base where it could cause a rear main seal leak more easily.

 

What Dave said. Long as you have plenty of pressure no need to worry.
Why are you changing the pan? Gasket? Have you replaced the O ring on the oil filter adapter? That can sure look like leaking pan and is alot less work.

 

It has no oil filter adapter, what it does have is a b-b sized rust hole !

 

Ah, yes! Here's something that might ease your mind. I once bought an 83 Chevy truck with a good running 305 in it, but the whole bottom of the engine was covered in thick hard-packed sludge. I started scraping it off and it got wet. I turns out the sludge was sealing multiple rust holes in the pan!