I think I'm done

I bought my 07 Classic just about a year ago, 65k miles on it, 5.3L V8. It's been a project since I got it, at first just cosmetic and maintenance things, but now fixing it has become a regular thing. I was really excited to have my first pickup, thought I did all the research I could when I bought it.I traded in my '13 Civic SI with only 25k miles on it. One of the reasons I did that was I figured the gas would equal out. The Civic needed 93 octane and I figured I could get by with 87 in the Silverado. Nada, after a month or so of 87 I started getting pre-detonation knock under load. I think I went through 2 Seafoam treatments and some fuel additive before giving up and just going 93.

So now I've done about all I can to track down this bad 1-2 shift. Afraid the next step is to either rebuild or replace the transmission. To keep the cost down, I'd probably end up having to do it myself, even then I'd be looking at at least a grand in parts, assuming it doesn't end up worse afterwards :? I think I may just put it up for sale, get what I owe on it and put that $$ into something else, maybe even Tacoma or Colorado.

The list so far though is:

New touchscreen head unit

New front speakers

New 12" sub and custom enclosure

New Kicker amp

New alternator

New throttle body

RC 3.5" lift

Window and hood deflectors

All new LED lights except hi/low beams

New dash lights and dials

Cabin air filter added

Back seat fold down mod with gun rack

Catch can

Custom CAI with Airaid MIT and Spectre cone filter

3.73 Gears (up from factory 3.23)

Transgo HD2

Sonnax Pinless 1-2 and 3-4 accumulator

Corvette Servo

Lew Tune

My wife suggested just selling it and getting something that I don't need to work on. I'm beginning to agree. I want something that's going to last and this transmission just doesn't give me any confidence.