I rang a reputable auto place today and found out a few things.

1. The JATCO box is very comon in lots of cars from mazdas to nissans to holdens, even VL turbos run the jatco with an overdrive setup infront of the box but the first three gears are the same. So its a very strong box (proably unbreakable with an a12) there would be no problem running these boxes behind an a14 or a15.

2. Fully manualized valve bodies are purchaseable and they even reverse the order of the gears (ie instead of it being N D 2 1 it will be N 1 2 3(D) which is better for racing) But this is too expensive for me, I was quoted $1000 supplied and fitted so it looks like I will have to look into making more vaccume (with the canister thing first then if that dont help I will tap a thread and put a vaccume fitting into the other side of my manifold as well)

Cheers everyone so far.