Is that mid-engine conversion for real or just a joke? I was in his shop late last fall and didn't see it (and he mentioned that his truck hadn't changed in ages)...
Kinda a loaded question.If you move it to far back it will be a wheel stander.If it was me i would research "altered wheelbase cars".What you are doing has been around a long time,As far as engine placement to better weight transfer.
I think I would move the engine a little farther forward. Put the balancer just in front of the crossmember. If that car is what it looks like they have a ton of rear weight with a SBC in them and the SBC doesn't sit that far back. When I used to race those things my car had 57% + rear weight.
You could go as far back as you can to mate the trans to the rear...unless rules dictate differently.
Just want the motor low and the line of the crank kinda pointed slightly down a degree or 2 .
Oval racing has rules and they usually won't let you go past the upper ball joint with the #1 exh port/or the bolt..
Road racing...depends on what class
The rules in pro street were that the engine had to be in the stock location and the fire wall had to be in it's stock location, but I don't think there are rules in this class anymore!