In addition to this question, now I have more. I started thinking that this may not be the path for me, that maybe I should just stick with the manual as I've had stick cars all my life, just need to man up and live with it. So I start looking into replacement options, and it gets ludicrously expensive fast.
1. Does no one make a beefed up direct replacement to the factory T-45?
Yes, www.thet45source.com will rebuild your T-45 to be good up to 600ft lbs+ with a 26 spline input shaft and slammer shift forks.
2. Or are you stuck spending $4,000+ on a magnum kit, or some other swap that will entail custom work?
No, see above. I personally think the T-56 is a waste of money unless you are going for all out top end and need the .50 final 6th gear ratio found on some T-56s
If I do end up going automatic, these are my remaining questions:
1. If I can't find a 98 transmission, how do I manage speedometer adjustments?
If you have a 4r70w without a VSS provision, you can swap a VSS provisioned tailshaft and housing yourself and they go for about $75 for the both of them on the evilbays. Or you swap to a 99-03 computer, ECU/Engine/Trans harness. Or if you are doing the 75w like I am you swap to the 04 stuff. You can also TRY to use an extended range speedcal to convert the OSS signal to VSS
2. For the ECU and harness, I'm guessing my only option is used, and it has to match the year of the transmission?
If you pay new, prepare to lube up... Used is fine just gotta make sure you are buying stuff with all the connectors in good shape and the right ECU.
3. How necessary is a transmission cooler if I'm sitting at about 300-310 WHP? I ask because the last thing I need is one more thing blocking my radiator (that's where they sit, right?), since I can barely drive the Mustang during the summer due to heat.
Biggest trans cooler you can fit in there should go in there. Properly setup, there should be no reason you can't drive your car even in extreme heat.
I think I misunderstood when you were describing what you're doing, Scotty. For your swap with the SYM2, you need the full wiring harness plus the ECU, and that will work with a 4R70W and/or a 4R75W?
What I am doing is using the best OEM computer available and a better starting transmission in the 4r75w. The 70w and 75w are not plug and play with other platforms. The 04 computers have to be tuned differently as the 75w has a different ring gear.