When I say stock clutch... I mean stock bellhousing from a 59(You could use any v8 chevy truck bellhousing up to at least 1972. 1968 and later truck bellhousings are already indexed to 5.125, so you might avoid some of the machining mentioned above), stock fork, stock pressure plate, stock clutch disc, stock throwout bearing (some machine work required on the transmission bearing retainer), Stock linkage... You may be able to use a flywheel with a 12 inch clutch (I have an 11 inch clutch in my 59 gmc with pontiac V8.)
The bellhousing crossmember does not need to be modified.
However you will probably want to fabricate a new tail shaft crossmember.
If you have a carrier bearing crossmember, that one can be eliminated.
The NV4500 pushes the shifter about 6.5 inches back from where the shifter would be for the sm420. (GMC V8 motors sit about 4 inches forward of where the chevy V8 and six cylinder motors, so my shifter is forward of where yours would be in the cab)
