/6 to 318
If your talking auto ( I don't think you are though) then it wont work....you would need a small block 904/727.
however though, I don't see why with a stick car you couldnt pick up a v8 bellhousing and flywheel and what not and be just fine.
the slant 6 tranny might have a lower set of gear ratios than one that might be behind a v8 but should be fine and you could always change rear gears down the road to better match the gears in the trans if thats the case.
im not 100% on any of this so ill let others chime in....but I think you should be fine.