[c_silva88]

imo- in my opinion. i didn't realize it was 4wd if you were to change the rear you'd have to change the front gears also so the cost would be more. as far as comparing horse power and torque granted these are newer engines but you get the idea horse powers higher in the 302 but torques close enough to not notice but in the 4.9 its a little lower rpm.
1988-91 4.9L EFI - 150 hp at 3400 rpm, 265 lbft at 2000 rpm
1988-91 5.0L EFI - 185 hp at 3800 rpm, 270 lbft at 2400 rpm
a transmission swap would be a good upgrade there are 2 options for a 5 speed there is the zf which has a low first gear good for towing found in f250s and 350s and then there is the m50d-r2 which is a lighter duty 5 speed found in newer f150s. both have overdrive and give you more gear options to keep the truck at the optimal rpms.
ZF S5-42 Close Ratio:
R: 3.79

1: 4.14
2: 2.37
3: 1.42
4: 1.00
5: 0.77

ZF S5-42 Wide Ratio:
R: 5.24
1: 5.72
2: 2.94
3: 1.61
4: 1.00
5: 0.76
M5OD ratios:
1st 3.90
2nd 2.25
3rd 1.49
4th 1.00
5th 0.80