The 5-speed boxes that attach to a M110 have 1st ratios of ~3.9:1, and a 5th of ~.8:1.
2.88 x .8 = 2.3; that is a very tall top gear to try to pull with a 2.8L engine.
2.24 was used with the 560 V8s, but not in the USA.
A 3.07:1 final may be worth a try.