LSx Valiant Build. Take a look inside...
do you remember year/model/motor it came in?
For readily available sources of the Chevy pattern 904 check
www.car-part.com and look up the 1980-1983 AMC Concord, Spirit, with the 2.5L, AT, or the 1982 DJ5L postal jeep as the search parameters.
For example, I turned up 35 of these 904 transmissions using the 1982 Concord/2.5L/AT as the search parameters. The prices ranged from $50-$225 + shipping and core charge.
Try to get the converter and the flexplate. Just like on a TH350/400 you will probably have to use a .400 flexplate spacer as LS engines do not have the extra material on the end of the crankshaft like Gen I&II SB/BB Chevy engines.
The bellhousing is not removable. Here's a picture of the Chevy pattern 904. I posted this picture in the other thread as well.
Let me know if you have any other questions.