I have an sm420 trans, used chev pressure plate that matched eng, donor and disc from 60s era trans to match input spline. Mounted standard 1500 chev PU slave cyl with fabbed bracket. Used same location of trans and transfer case as front and aft spacing of eng. worked well, no changes to drivelines, already had SYE. Exhaust interfered with slave cyl so used manifold from full size van for more forward dump, then routed front of oilpan to pass side. Custom header may be in future as driveline still rubs, will consult exhaust professional before going furthur with exhaust. Lincoln electric fan.
By the way where did you get your ECM reprogrammed?