BA Vs BG Engines could be sticky, but more people should add to this 

BA 
block has NO oil cooler 
has no water or oil lines for turbo 
has single counter weight crank 
has big nose crank 
No main bearing support plate, just a spacer 
Ali finned Sump 
has 9.1ish pistons (slight rise) 
has 3 selections on the cam gears, I E and Z as a notce in it 
has BP05-10k head 
BP05 inlet and BP06 exhaust cams 
has different valves, same mm's I don't know 
has different valve retainers 

BG GT pre-cat 
9.8:1 Pistons 
BP05-4k head 
same Valves etc as GTX 
has different TOP piston ring, 2nd ring and oil rings same as other BP's 
has Dual counter weight crank 
has main bearing support plate 
has big nose crank 
Ali finned Sump 
BP22 inlet and BP05 exhaust cams 
oil cooler 
water and oil turbo holes 

BG Japspec etc 
8.9ish Pistons (9.0:1) 
BP05-4k head 
Same valves etc as GTX 
dual counter weight crank 
small nose crank, and big nose (depends on year) 
Main bearing support plate 
Ali finned Sump 
oil cooler 
water/turbooil lines 
bp05 inlet BP06 exh cams