Time for a new truck?

[D13]

99 sierra 2500 5.3 4L60E 14bb sf 145000 miles. Truck sat for a year, then had to do brakes, replace plugs and 2 injectors. Truck has gotten less than 2000 miles in past 6 months, haven't started it since December. Cracked windshield, drivers rocker rusted off this winter (while sitting!), getting rust over wheel wells and in tail light pocket. 4l60E shifts fine but TCC wanders in and out. Has low voltage reference on bank 2 sensor 2 O2, replaced sensor not the problem, so either bad wire or internal short in PCM. Now it's setting misfire code for #8, can feel it misfire under any type of load. So I'm looking at:
windshield $600 (all the j-yard ones are broken too)
Trans either solenoid ($100 and having to pull exhaust to get to it) or converter ($1200 cause if it needs more than a solenoid it's gonna go 4L80E)
Injector ($125, it's the first style that no one bothers to rebuild, if I use the cheaper later one I need 8 + a tune) or coil ($65, it's a first design)
Both rockers and paint - $500 (beyond my feeble bodyman skills)
Paint tailgate (from previous issue) -$100

So If I dump $1300-2300 into it I;ll have a 150k mile 99 that gets 16mpg.

I'm thinking maybe I should get my 87 diesel running, pull the motor and sell the brake parts and just scrap the beast. the only issue is the occasional need for seating for (if the minivan goes into the shop), and I figure we can just stack them in.

Opinions?