Here’s the thing, and I’m going to be blunt and honest so suck it up butter cup, your screwed.
Now, how to get around being screwed and tattooed!
The first problem is you want it all. This will require an OD trans for a reduced rpm cruising. Now to smoke Mustangs, what Mustang are we talking about?
As an example, the A-500 has a good first gear for a good get up and go off of the line and a reasonable OD ratio for Hwy cruising.
Regular 904;
| A-904 / 30RH | 2.74 | 1.54 | 1.00 | N/A |
727
| A-727 / 36RH /37RH | 2.45 | 1.45 | 1.00 | N/A |
Notice the first gear ratios. Your looking for a 10.00 ratio via first gear ratio and the rear axle ratio for best off the line performance.
3.91 X 2.74 =10.71
3.73 X 2.74 = 10.22
3.55 X 2.74 = 9.727
OD (.69) X Gear ratio for final drive ratio;
3.55 X .69 = 2.4495 (I’d call it a 2.45.)
3.73 X .69 = 2.5737 (2.57)
3.91 X .69 = 2.6979 (2.69/2.70)
Find an on line calculator to work with the final drive gear ratios and your tire diameter for probable cruise rpm at what ever speed you realistically drive at.
I hope this helps in an easy cruise rpm and getting off the line.
Now to find a guy that can build up your A-500 to hood the power. The nicer thing about the 904 & it’s variant’s (A-500) is they require less power to turn than a 727 & it’s OD variants. That means more power to the pavement and better mileage.
