gear ratio questions,89 mh613

[superliner237]

Hey guys! I'm havin' some issues with what gear to go with on my ongoing project 89 mh. lets start with what i have and think i know. 89' e-6 350,4valve hooked to a .71o.d. 2090. i have 4.42 gears with 24.5 tall rubber. new tires seem to be 44'' tall.rolls dn road really good. likes the 65-68mph range in over gear. come to any hill, long drawn out ones are the worst, and it falls off boost but still is too fast to grab direct. overall gear too high i know. what i have to work with and what seems good on paper is a set of 3.65 rears and a 1989 1070b 12 spd. Never had a working tach in this truck yet. And no i'm not going to put a eaton 13 in here. the eatons i have are .78 anyhow so im going to keep it all mack. the 3.65 gears are in my 79 cruiseliner. light truck it seems so i will assume they are 34000 lbs. all i can find for numbers are..11kha5327 p17, up high on carrier. 93 9j2233 towards bottom. truck had 300plus with an eaton direct ten on neway air, not like that matters. i run this truck over the road and would love some input from you guys on what you would do in my situation. I pull 75-80000 most of the time withe some oversize weirdness mixed in every so often. also, i really like how it is now, just wish i could split gears. i think that would put a really big smile on my face. hope you guys can learn me something on this topic. thanks for anything you give me.

[mack mhe9]

The set up i like, put 3.65 in it. a mack 18 or 13spd cause you don't have to cut the drive shaft. And 24 low pros. Then I run in 17th that 60mph at 1500rpm. The 13 or 18s a nice split when the eng's down around 1400 on a long grade in 17th gust split the gear and your right in at 1650 in 16th that's also direct so all your power goes through the main shaft on a pull. You still have 18 th for when your light or empty, hope this helps