best 340 tranny??

Could always rebuild the 904. Could buy a diy kit w/ a shift kit or send to a tranny shop. If the 340 is a basically stock or mild build, wouldn't be expensive at all to make the 904 handle.

I ran a 904 behind my 450hp small block for about 5k miles before I tore whole car down for rebuild, great transmissions. (EDIT: Only cost me about 1,500 to get my 904 built to handle the abuse of my small block with small amounts of spray. So for a less powerful engine, could do it for ALOT less)