8.25 gears in a 8.75

Ok, I know this is an odd ball question, so bare with me. I have a project that I am starting and need as high of a rearend gear as I can get, but an 8.75 is limited to a 2.76, and I need higher than that, like the 2.24 that came in the 8.25.

Ok, the reasoning is that I am putting a 4bt in my Dart, with an NV4500 behind it. But, to keep the RPMs down in the teens as the 4bt is a diesel and does not spin high RPMs and I am doing this for fuel mileage, I need a good overdrive, with out going to a TR6060 that is built strong enough to handle the 4bt and costing $4,500 just for the trans.

The question is, has anyone heard of people putting 8.25 into an 8.75 since I need the 2.24 gear that comes in the 8.25. It has been done and that is what gave me the idea to do it instead of the expensive tranny and would let me be in gear for longer. But, the problem is I can get ahold of the guy that did it and I have no idea what was done for his machinist to get the gears in the 8.75 housing.

If someone has any idea how this is done or how you would go about it, please let me know.

Thanks.