320HP Magnum Crate w/ X-heads

The parts hoarding continues!

I am purchased a new 320hp Magnum crate long block from Summit (thanks @Heywodja ) for my dear old Dad.
ATK High Performance Engines HP73 ATK High Performance Chrysler 360 Magnum 320 HP Stage 1 Long Block Crate Engines | Summit Racing

Back Story: I had previously given him a 1972 360 block and many parts for his "70 Cuda. Basically everything minus rotating assembly and cam. I helped him source a 6 Barrel manifold and a set of X-heads. I am working with a car builder that knows the owner of Fi-Tech to get a sponsor discount on a 6 Pack EFI deal. The manifold and X-heads are at a machine shop friends and they are getting a little cleanup and port matched. Going with a 224 @.050" cam / LSA ~ 110 degrees. He will be using the TKO 5 speed out of my '70 Cuda.

Well, this Magnum crate motor popped up and being that it is already machined and it has factory hydraulic roller lifters I called my Dad and asked him if he wanted me to pursue it. Got the green light. I really wanted to keep the good 360 block and parts I had been collecting because I eventually wanted to build a 3.79" stroker. The crate Magnum engine gets him a little farther faster and I can get my parts back!

So here we are, we possibly need a 360 piston that is going to work with open chamber x-heads.
KB KB191KTM-020 Keith Black KB Performance Hyper Piston and Ring Kits | Summit Racing
That is if they are needed. Ideally, Dad want's around 9:1 compression. The whole reason for dumping the very hot 440 and going small block is driveability. He wants to not worry so much about crappy fuel. EFI and 8.5:1 - 9:1 compression should ease concern and the 5 speed and 3.55's should allow him to drive however far his wallet can stand.

The advert from Summit says it's from ATK and they use a seasoned block. I figure we could sell the heads and valve covers and get a set of pistons. I reasserted that this crate engine would need to get disassembled and inspected anyway so it would be a perfect time to measure and get the right piston. I kind of had to educate him on the Magnum/LA difference in oiling too. We'll just just use the pushrod oiling and keep the lifters. Will swap the cam pistons when it gets torn down for inspection.

A couple of thoughts and things to question:
What would the results be with putting the x-heads atop the piston's in the engine now? I guess we just have to measure but I am sure the pistons are in the hole a couple thou. The trigger for buying new pistons will be if the compression will be 8:1 or lower. Should we move the trigger point to 8.5? What's the thinnest gasket you could go with on a lower comp engine to bring up the compression?

Pushrod oiling. I am expecting to just need to get different length 'oil thru' pushrods. The x-heads will be using the Mancini branded Harland Sharp adj. rockers.

Any other considerations for this Magnum w/ LA heads deal?