I drive mine sometimes on the street. 438"w, methanol injected, PG, 6000 stall spragless. It's a bracket car not a heads-up spend as much as you can to beat the next guy.
It drives just like a C4 but without first gear. WIth methanol injection, it runs rich at anything under full throttle anyway, so it's real choppy, stinky, and VERY responsive. The PG's low gear (which is similar to a C4 second gear) takes up a lot of that jerkyness at low speeds/part throttle. I'd say it's streetable but everyone's setup is different.
Again, it's similar at part throttle as a C4 in 2nd. Similar but not exactly the same. PG has a little lower low than a C4's second (1.80/1.82/1.76 PG vs C4's 1.48)
PG eats up a little less power too and built correctly they are VERY robust. I'm on season #13 with mine and I ain't nowhere easy on it, no rebuilds in that time period. Street miles? Maybe 100. Trailer it close to the "drive", then unload and drive it to the spot. Usually under 5 miles or thereabouts. I had the pan off this past week doing inspection for excessive mud or metal; none found. Replaced fluid and wanted to run today, 70% of rain dampened that-and guess what? Not a drop fell from the sky. About right.
I went from 4 speed to a PG (same day, different cars) and the PG is almost as much fun, particularly if the car runs faster than 10.00 (give or take). 4 speed car was 9.40's and PG was 8.90, real similar engines but the cars' weights were different.
I've raced PG equipped cars from mid 13's to 8.80's, all N/A, and I've run (personally) C4's from mid 14's down to 8.90's n/a in my own stuff. Prefer the PG but again I'm bracket racing and some index stuff. I like mine but again I don't do much street with it. Keep in mind that back in the 1960's and early 1970's, these WERE street driven, behind low powered inlines mind you. People liked them; but some found success in swapping in a "new" (in those days) TH350 short tailshaft which was a bolt-in deal minus shift linkage and kickdown cable. The aluminum powerglide is one of the few things GM got right, and even then, they aren't "perfect"--but the aftermarket.....gosh you can actually build one without a single OE part nowadays. Hard to beat one for a bracket racing combo like mine, at least if it's properly set up.
Lotta guys say go with a TH400 and they are good transmissions, but heavy--and they can get really expensive real quick. C4's need a lot of mods to live; and even then there's no guarantee. I've run them for seasons between rebuilds, then the next one might get 15 passes until it smoked the forward clutch, or whatever. Those were mostly low-buck builds as well; nothing exotic, not a lot of aftermarket internals other than valve body, servo, and clutches.
The bad part about 3+ speed stuff is that once you start making some real power, especially in a light car, it gets to the point where traction becomes an issue and/or wheel stands can get out of hand, negating a wheelie bar (or as some call them, sissy sticks), making chassis tuning imperative.