318 motor + 904 Tranny

The 727 will fit but you have to hammer the body crimp seam flat with a hammer in the tunnel entrance. Not hard to do. The 727 is 4" longer so you'd need a 4" shorter drive shaft but certain trucks got a shorter tailshaft 727. Not sure what trucks. HD 318's (318-3) may also have: double roller chains, lower compression pistons, steel cranks and sodium exhaust valves + rotators on the springs.