Once they are set up right, they love you long time.

On my 81, most of the fiddling came before I started reading posts here from guys like boyt911sc, psalt, osssiblu, john walker, etc. Then I fixed (vs fiddling) the issues.

When working prop (CIS), mine always has on 2 dif SC motors, they work great.. excellent response thru the rpm range, no popping or flat spots like carbs do, and nice mileage (23 mpg in town presently).
I've had a few P mechanics tell me that it also keeps the heads cooler than motronic and in their opinion that was part of the 3.2 valve guide wear issue...

with a 20 k budget I'd focus on an 84-89 3.2, but if a really nice SC comes along, I wouldn't discount it.

I've owned both, I really like the motronic system but as stated, properly running CIS is just fine.

the sweet spot for you may be an 84-86 car, coupe if you can find one.

As stated, reliability on these cars when well maintained is excellent. I drive my carerra, with 146k on the clock to work 3-400 miles/week during the nice months, and did the same with my old 83sc, and an 82 targa before that.

good luck!!

I've owned my 84 3.2 for almost 3 years and have had no issues whatsoever. Its a g50 car with some fueling and electronic mods(injectors, chip, larger valves) etc. I have had no issues with anything really, it starts up every time, and runs great!
I don't have much experience with the cis SC cars, but I guess you can read and read and begin to overanalyze just about anything. I didn't do too much research on the car I bought, and probably got a little lucky. I cannot say anything against the SC, but like others have stated the newer the car, the more improvements, and the possibility of more expensive repairs as well. Just drive it, and enjoy it! Its not the fastest or best performing vehicle, but it's the most fun to drive hands down.