Reusing stretched timing set....?

I pulled apart the front of the 318 in my '88 Fifth Ave to replace the stock chain and sprockets as preventative maintenance (would post on the FMJ forum but way more engine experts here). I wanted to reuse the double-roller timing set I pulled off my busted 360 (broken piston ring land) with about 25k miles on it. It does have quite a bit of slack, close to 3/4" which I have read is supposed to only be 1/2". Thing is this car is strictly a driver/cruiser and I don't want to spend any more than I need to; I already bought a new OEM replacement harmonic balancer for $80 because the old one had badly deteriorated rubber and IF I do get a new timing set I'm going for one of the better-quality ones which run around $150... Keep in mind I bought this car for $700 lol.

My idea is to also swap over the timing chain tensioner I had on that 360 to keep the chain from bouncing around, set the crank sprocket keyway to give +4 degrees of advance to make up for the slack in the worn timing set and call it good. What do you guys think? The engine is all stock internally including the cam, I am converting from 2-bbl Lean-Burn setup to a ThermoQuad on a Performer intake but even then it'll barely rev over 4500 RPM with the stock cam.