First off, is it an extended block or not? Makes a huge difference.
Extended:
View attachment 1716276464
Not:
View attachment 1716276465
If it's an extended block, try WilCap (
https://wilcap.com/index.htmlor) or HotHeads (
https://hothemiheads.com/transmission_adapters/index.html) for adapter kits. The adapters are for 727s, but they work with 10" convertors, so you may get them to work with the 904.
If it's an extended block, good luck. Sorry.