i don't drag race my 109 either (just in case you don't know, it's Big Ears) the transmission is too sweet to abuse and he's a nice straight truck that i expect to own for quite some time
3.54 diffs only at present which gives me nice cruising speeds along with pretty fair economy of roughly 29.3 mpg over 220 miles averaging 60mph with a high of 75-80mph for a short while this weekend, 99% of that journey was motorway
no idea how come your engine sat so high, mine sits nice and low in the chassis in both my 88" and Big Ears along with the same in the '59 88" i'm building at present, i'll guess your chassis mounts have been relocated at some time for some reason