Hey Bill,
I think I know what you have in mind in regards to tying the subframe and fenders into the chassis better. The one thing I was concerned about and that deterred me from doing the RB26 swap on my car was not only the money (about $7000-10000) but also chassis rigidity. The RB26 is a much, much bigger motor than the SR20 and you need a lot more bracing than is required with an SR. I know for a fact motor mounts will be an issue as I noticed even with McKinney mounts my RB20 still twisted my drive train a little on tip ins. I hope you are going the solid mount route as you will be much better off in the long run.
As for the ECU, a reflashed GTR ecu is a good idea and I know PUR Automotive are very good in regards to getting the most out of stock RBX ecu’s so you should look to them. If you don’t mind me asking, why are you going the PFC route and not an AEM full standalone unit as there is not that much difference in price if you do indeed go with the higher end PFC. Or is it because of the fact you want live streaming data as a trade off for the local tuners being able to tune it. (I’m a guy who prefers quality over features, and that is why I suggest the AEM as it’s pretty much a one time tune and well worth the $1800 imo).
I am happy you have sorted out a majority of your driveline, the Kaaz 1.5 way or the S15 Helical Diff will give you a much better feel of the car, and as for the half shafts, you should put the upgrades in before the car is even roadworthy as I know 240 half shafts aren’t the greatest. Also, I am glad to see you’re going big single on it… it will be a hell of a fun drive… and I am itching to see it especially since you will not be having the crank collar issue (although you should still upgrade you Oil Pump right now for safe of mind. ;))
Congrats on the swap choice and best of luck carrying it out! Car is looking good already.