I have a 80 liquifire, 79 invader and 80 4/6 engines apart in my garage. The liquifire and 4/6 pistons are nearly identical - same rings, pin position, weight, domes. The invader pistons have diff pin position, rings. The stampings between liquifire and 4/6 are different, and the only physical diff I can see is the 4 small hole drilled in the wrist pin mounts from the bottom. and, some 4/6 pistons have a coating.
I am right here. 4/6 pistons are typically hard to find. Why not use liquifire pistons.
I have kawi mono head pistons and jugs as well. Pin position on these is same as invader. Porting on all these motors is very similar except for the extra boost port on 4/7 and 2 on mono head.