The roller blocks, both LA and Mag, have taller lifter bores and also threaded bosses in the middle of the valley to bolt the lifter retainer spider to. The taller lifter bores have reliefs on the inside of the pairs of lifters that allow the dogbone pieces to hold the lifters.

I would just look for a 5.9Mag block, they are 10 times as plentiful as the 360 roller blocks.

AFAIK all four roller blocks use the same lifters and retainer hardware. Chrysler was not interested in adding expenses when these engines were built.

R.