I think the oil pan from an 8.1 vehicle like the 2500/3500 trucks would work on this being it's a Gen 7 based block.

Correct.
Its my understanding that the PSI 535 and GM 496 have the same pan rail bolt pattern... so the 496 pan and pump pickup should swap over to the 535 without issue.

Im going to start shopping for small parts awhile.
Can anyone tell me what ARP studs will fit the heads and mains ?
I assume the head studs are same as stock 496... and main studs are same as Gen4 big blocks (1/2" std threads) ???

And in response to the earlier comment about the exhaust manifold fasteners... it does appear to be an 8mm metric thread.
I have a Bridgeport in my shop... and might just convert them all over to 3/8-16 like they should be.

Also trying to figure out how to make the valvetrain adjustable... since it currently uses non-adjustable LS7 rockers.

The 496 Gen 7 has metric main bolts (stamped 11.9), so I bet that PSI is also metric. The cool thing is all the main caps are 4 bolt, even the ends.

Just buy Metric head bolts for the 8.1/496 from ARP. I bought mine from Summit, but you can ask ARP, they have them.

Do you really want to start converting to SAE? Everything on this engine is metric. The metric bolts are easily obtainable for every part externally and the internal stuff is available from ARP as well. That will get messy when you start bolting up all the alternator and closed cooling stuff and half is metric and the other half is SAE..

As for the rockers, yes they can be converted to adjustable rocker arm nuts but then you need new valve covers since the nuts wont have the clearance. Again, the bolt and go rockers seem crazy, but they work, and there are a jillion 496's in the field that run fine and even in a performance app like my 600's - they work fine after hundreds of hours.

I agree with Keith's advice. I ran the Raylar bolt on stainless rockers in the past and they worked great. They fit under the stock valve cover which is sure easy, as there aren't any aftermarket covers available for this engine.

If you do want to go adjustable you can, I did with a set of T&D rockers on Raylar heads. I had to use a 1/2" Medice Mfg spacer to make it clear the stock valve cover. The factory exhaust cleared just fine after the spacer install.

That looks like a nice set up.

What did you do with the coil packs? Are the plug wires long enough?

The plug wires were plenty long, coil packs in stock location. With the Whipple the plate for the PCM gets moved a little anyway and it all worked. You can see the cover spacers in this picture. This is a Raylar 800HP package except for the upgraded rockers.

Note: That oil filter is not plumbed in, I run a remote mount on the transom. All high flow stuff.

^^^^^^ I assume then the Kmart filter is for shock value when hatch is popped.