Hypothetical 318 Commando Build

And on that note; recall that Op has 3.23s, so 5000 in first gear with 25.5 tires comes to 44 mph.
OP said; would be nice to have more torque. To me that implies less-lazy at take off, not more power at 5000rpm.
The 318 was born making more low-rpm torque. To spice it up even more, requires one or more of;
1) more cylinder pressure at that low rpm. or
2) raise the Stall to convert torque to horsepower. or
3) more rear gear to make the engine feel bigger than it is, in first gear, especially at take-off.or
4) weight reduction
What happens at 5000rpm/44 mph, is of less concern.