A few questions

I would modify/clearance the pan before hacking up the frame.

The 8 qt milodon fits, just lop the front pass side corner off and weld a flat piece in place.

The slant k frame is Identical to the small block k frame with the exception of the pass side mount, it need to be brought foward and up some, the driverside is a direct bolt up to a sb motor bracket.

The lifter angle casing loss of lift can simply be compensated for with more cam lift, say the average loss is 5% of every .100 , so .500 lift loses .025 lift...add that much more to the lobes you choose. Mock it all up after machining and short block is done with heads bolted to block w/head gaskets and see what the % of loss is per .100 with any cam you have laying around to get an idea of how much for certain.

Really...with a closed chamber, the iron head will allow about the same if not the same compression an aluminum head will allow on pump/limited octane, it's only a weight diff...and with all the same...the aluminum head needs about a full point more to make the same power.