A little help?

If not full exhaust a set of headers/x pipe. Beyond that I'd likely choose a set of heads next with the mods you list already.

On a budget? do the junkyard upgrade...

Gears - 87-88 T-Bird Turbo Coupe rear axle - 10.5" vented disc brakes and 3.55 or 3.73 gears in one package for $125-$300. Uses the stock 4 bolt lug pattern. Add another $100-$200 or so to complete the brake upgrade.

94-95 Mustang GT MAF - $40-$100. It is 70 MM instead of the stock 55 MM on regular stangs built prior to 94. It uses a slip on duct on the side that goes to the throttle body and a 4 bolt flange on the other. You need a flange adapter to fit the stock slip on air ducting that goes to the air box. Wiring plugs right in with no changes. *1 *2

95-97 Ford Explorer intake manifold & throttle body $150-$300. The intake manifold flows 220 CFM +, much better than stock. Throttle body is 65 MM, bigger than the 60 MM on stock stangs. I got a 96 with EGR passages that match the stock setup, so my smog gear works just like factory. You’ll need a 65 MM EGR spacer & new gaskets for $65-$90 so you have a place to mount the EGR & throttle linkage.

3G alternator from 94-95 Mustangs or other Ford. $20-$120. A must have to make the electrical system work like it should or if you have an electric fan. You’ll need a 4 gauge power wire and a 125-135 amp fuse to go with it - about $25- $50 for the wire, fuse holder and fuse.

Lincoln MK VIII electric fan -$40-$160. Free up some HP by not having to drive the stock fan. The 3G alternator upgrade is a must have prerequisite before you do the MK VIII fan. You won’t have enough electrical power if you don’t do the 3G upgrade.

Aluminum driveshaft: (courtesy of shawn13) It needs to be from a 92-95 AeroStar AWD or Electric 4 wheel drive. It measures 45 ½” center of the front U-joint to center of the rear U-joint. You will need the U-joint, part #PUJ353 from NAPA. The Canadian NAPA pat number is 1-0134BF. It should bolt right up after the U-joint swap.

bhuff30b’s input: However, no information was given for the 96-97 AWD aerostar driveshaft. I picked up one of these this weekend, for about 20$ from the local scrap yard. It already has the proper 27/28 spline yoke and needs no modification to install on a mustang. Also, the ends are securely welded on, as opposed to previous driveshafts which were pressed on. I'm not sure if the 92-95 driveshaft is pressed or welded though.

Note: This driveshaft is not an exact duplicate of the Ford Racing part. It is 3” in diameter while the Ford Racing part is 3.5” in diameter.

*1.) Metal flange adapter Kurtz Kustomz Motorsports, Inc. KKM Buy the TR70 for $44.95. Or spend some time on eBay looking for one that may fit.
Try AutoZone and ask for 81413 - Spectre / 3 in. Aluminum Intake Mass Air Flow Sensor Adapter at $12.00. You may have to order it online.

*2.) MAF & sensor interchange
The 94-95 Mustang 5.0 MAF & sensor is also found on:
1994-95 Mustang 3.8L F2VF-12B579-A2A,
1992-94 Crown Victoria 4.6L F2VF-12B579-A2A,
1994-95 Mustang, Mustang Cobra 5.0L F2VF-12B579-A2A,
1992-94 Town Car 4.6L F2VF-12B579-A2A,
1992-94 Grand Marquis 4.6L F2VF-12B579-A2A,
Evidently the –A1A, -A2A, AA, etc. on the end of the part number is a minor variant that did not change the operating specs. You should be able to ignore it and have everything work good.