Slant 6 to 318 swap, 72 Duster, Using 75 D100

What about the trans bolt up? Same pattern on thr v8 & /6?
I have a 73 i just picked up n wanna do the same. Although i read on wikipedia
That certain 1975 set ups could get you like 35mpg hwy.
Thats sounds awful tempting for a cool old cruiser too.