What would be the best transmission for a hybrid B20 block/B18C head engine??

 

Depends what you're going to be using it for... its all about personal preference...
I'd go with an S80 or a Y21... nice ratios, not too close, but close enough...

Throw a Quaife on it and you're all set

Sure you could use an LS gearbox with a hybrid final drive or something like that, but its effect probably isn't worth the trouble...

 

gsr tranny with an aftermarket final drive to your preference..

good gear ratio