Keep in mind that with the OD, your real rear ratio would be like a 2.79. That will push the converter real hard, and if it is a higher than stock converter you will see quite a bit of slippage. In a stall converter test article using different rear gears the rpm didn't go down a lick after going a 3.55 gear. Below 3.91 started to show too much slippage to be worth it with the converter they tested. A better alternative might be a 904 with the lockup converter and something close to a 3.55, and if it would work for you, a 3.55 would put you at 3,000 rpm at 70 mph with a 27.5 inch tire. Or 2600 at 60 mph. The lockup could be set up to only work in high gear, high vacuum to avoid hurting it. this would obviously also save you the aggravation and expense of drive shaft mods and tunnel clearance issues.