I have an early (60's) V8 bell housing that bolts up to the SM420 and is set up for the mechanical clutch linkage. This was in my '62 C10 when I bought it, but the engine had been updated to a '67 250 straight six, same pattern as the SBC. I converted the truck back to the factory hydraulic clutch when I put the 327 in so I had to swap out the bell housing for the hydraulic set up.
I don't remember the casting number on the spare bell housing, but I'll look at it in the morning and post it for you.
