273 or 318 or both help

IDK guys;
1) the early 273 had lightweight floating-pin rods, 3.63 pistons, and I think a forged crank.
2) the 87 318 has heavier rods, press-fit IIRC, 3.91 pistons, and a big fat cast crank.
IDK if you can swap them without issues.

Ima gonna say that yes both are internally balanced, but balanced to the parts of each engine. I'll bet a box of mattress lint, that the bobweights are different. I have both cranks in my shop, and that 273 crank looks mighty teeny next to the late 318 cast one