I just put a ht383e in my 98 silverado. It has bbk tuned headers with cat free 3in exhaust with 14in magnaflow muffler and tuned pcm from blackbear. The stock tranny is not loving it and is starting to slip shifting from second to third. Talked to a local transmission builder and he quoted me 6000 to rebuild tranny to handle that motor. It seems a little pricey to me ? Curious what route you go would go? Thanks for your time
Prices are high there, and in most of UT (I'm in Vegas, have numerous customers in UT, especially the St George-Cedar City area).
I'd do a 4L80E...6k vs appx 4k and you'll have a much stronger transmission that will last a lot longer if you actually use the power your engine is now making. ..You'll need a segment swap to your PCM to control the 4L80e, a wiring harness adaptor (you can buy or make yourself), rear cross member gets pushed back and cut/balance driveline if you have a one-piece drive shaft...this assumes a 2WD.
PM me if you'd like more details on a build.