Probably the wrong forum so please point me in the right direction if there is somewhere better.

I'm rebuilding a TH350 that lost all forward drive after topping up the trans with dextron.
Box still went into reverse OK.
I don't know its previous history and It isn't original to the 'Vette it came out of, but it did drive on/off the trailer and in/out the garage several times until topping up the trans.

Initial indications seem to point to the forward clutch.
Pulled trans & pan was full of crud.

There was no spring in the 1-2 accumulator, (definately didn't jump out )
Only two checkballs in the valve body.

The box appears to contain red friction material so i presume it's been rebuilt.

Will/would either of these issues cause it to lose drive?
Is the spec on the accumulator spring critical? ( ie can i substitute it for something similar ?) Ebay + postage is about 30 USD to the UK?
Is there one in a TH400 that would fit?