Can You?? One of the systems to up grade for swapping in a Coyote drive train is the rear. The 73 currently has an 8" 3.25. I've recently found out that a 99-04 Mustang 8.8 rear axle is 62.25 in flange to flange(some resources quote 61.6125). The 71-73 mustang rear axle is 61.5. Stick a 99-04 axle in a 71-73, you have an extra 3/8" on either side which is purdy much within allowable tolerances. (folks have been sticking Lincoln Versailles/Granada rears in 65-66 Mustangs fer years and thats with an +.5" per-side) Using after market wheels?? Difference is easily changed with off set.
How?? I have a set of 200 Mustang 8.8, 28 spline axles and Trac-loc diff, soon as I can find a carrier, I'll do the swap. Essentially grind off all spring perch & swa-bar mounts and relocate leaf spring mounts for the 71-73 with reset pinion angle
Why use an 8.8 in a 71-73?? For the average hobbyist, prolly easiest/cheapest way to get; lighter rear axle, Disc Brakes readily available range of gear ratios, & Stronger Diff w/LSD (Limited Slip Differential - Posi/Posi-track is a GM term. Rather universally understood, however inappropriate to apply to a Ford unit) 8.8 is a close copy of a GM 12 Bolt, stronger than a 8", and with 31 spline axles almost as strong as a 9", larger pinion shaft is better than a 9's weak point. Now most (some do have 31 spline) 99-04 Mustang 8.8's use 28 spline diffs, same as 70's 9" rears. So, compared to a 8" the 8.8 is superior alternative; lighter & stronger, has disc brakes, prolly cheaper than rebuilding (How good are your scavenging skills??) Compared to a 9" close to equal strength, will have Disc brakes, and is lighter, means better handling. Worth replacing a Good 9" with No, cheaper than rebuilding a 9" Wellll possibly. Unless one of the 8.8 advantage reasons is particularly strong for you, Rebuilding the 9" is prolly Best.
August HRM has a Ford 8.8 Scrounger's Guide page112
