Differences in 904 sun shells

It seems odd that the sun shell would be made from thicker material but I guess it's possible.

This quote is from a Moparts thread started by Scott/dizuster when he made a post about swapping 904 parts.
I know this may not really answer your question exactly but it could help understand what's going on.

"Low gear sets can be switched out of late style 904's but the thrust plate that goes between the snap ring and the sun shell must stay with sun gear. There are at least 2 distinctly different thickness thrust plates in the sun shells."

everything you never wanted to know about 904's

I'd try to anticipate where your end play is before you put the front pump in.