I currently have 2 gearboxes for my hillclimb car which is 725kg and 220bhp n/a

before I put a decent box in I need to know what would be best for competition

1 is a normal series 1 lsd box, the other is a ib5 with st150 gears and series 2 lsd

The series 1 is
1st 3.15:1
2nd 1.91:1
3rd 1.27:1
4th 0.95:1
5th 0.76:1
Final drive: 4.27:1

The other box is
1st 3.58:1
2nd 2.04:1
3rd 1.41:1
4th 1.11:1
5th 0.88:1
Final drive 3.82:1

Which would be the best box to use as they are? Or is it possible to strip both mainshafts down and fit the st150 2nd, 3rd, 4th and 5th gears on the series 1 mainshaft?

Which would give
1st 3.15:1
2nd 2.04:1
3rd 1.41:1
4th 1.11:1
5th 0.88:1
Final drive: 4.27:1