First, I'd use the rocker ratio that the cam was designed for. The crane 2030/2031 cam kits are a great budget pick ($210 inc. springs). The split duration favouring the exhaust is good (although it may not be necessary with the off-road H-pipe)... the wider lobe separation angle gives you a broader torque band, moderate duration keeps cylinder pressure up, and the added lift gives you some good flow.
For a few more $$$ a mild comp cam extreme grind would be great.
Peak torque on a stock mustang is around 3200 RPM, that combo will probably put the peak around 4000 RPM.
I'm not a fan of FMS cams... not very agressive (long advertised durations, not enough lift).
You can get GT40P/explorer heads bare for $200. These have smaller ports/runners than the windsors... so they don't have as much potential, but they have AWESOME flow velocity, and provide GREAT low end. With the rest of the combo, they should outperform the windsors all the way up to the rev limit (on a 351, they start to loose out around 5500RPM).
Do a search, there's some great info on these heads.
Cheap valves for $75, or manley race flows for $195. You could do a bowl blend, exhaust runner cleanup, valve job & milling, and still be cheaper than the windsors (and perform better).
It seems like you wanna keep your low end... but if you wanted to trade off a bit for the top end, the Holley & edelbrock kits would take any guesswork out.
The stock MAF pegs the max voltage at around 330HP... so the 19# injectors and calibration will be alright... but the 55mm MAF is a little restrictive (5-10HP loss), so a bigger MAF is a good idea. I got a 24# calibrated 75mm Pro-M bullet, and use my 19# injectors at 61psi (=24#)... ya, I'm cheap.
Trick flow 1pc chromoly hardened pushrods are about $75 at summit... great price.
Also, the engine is only about 30% efficient, so even a modest HP increase means A LOT more heat.
I highly recommend the
www.stewartcomponents.com water pump. An SN95 or MarkVIII electric fan is great... keeps you cool at idle, and frees up about 20HP.
Forget the factory 5 control arms, unless it's just a drag strip car. Get some good lowers, and keep the stock uppers... or spend some more and do a torque arm & panhard bar or 5 link. The auto will certainly let you get away with less (you don't get the abrupt torque transfer to the chassis like when you pop a clutch).... you should have subframe connectors though.
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'89.5 5L LX, hatch, Medium Canyon Red, 155K Km (No winters), 5sp, 3.08, GT interior, a/c, Alpine CD, K/N, Crane PS91, Walbro 190 LPH, March Pulleys, Mr. Gasket 180 therm (HP balanced), 3 core rad, MarkVIII fan, Variflow controller, Polygraphite front bushings, FMS-5300B springs, 6 KYB's, 73mm Calipers, Maximum Motorsport 4pt chassis brace, Western Motorsport Racing's Sub-frame connectors. Re-ringed bottom end, conv. motor mounts, melling oil pump, FMS-C50 waterpump, GT40P heads (blended, polli