Henry's 70 Dart Swinger

Pretty much any COMP cam I've ever used prefers more timing than stock...hell, even stock engines like more timing than stock spec. 10* is a good place to start for a mostly stock engine, and I'm sure you have a vacuum gage to aide in tuning your new carb-good choice for what you're doing. I'd advise you to get the calibration kit for that carb to fully dial in what you want...unless by some luck, yours runs perfect out of the box. I used one for my old AFB Edelbrock and it helps the part throttle circuit-especially when it comes to mileage, if that concerns you at all. There are many folks who'll poopoo Edelbrock, but IMO, they're tough to beat for street behavior.

When I installed my 5.2, I bought a Summit 600 VS carb...essentially a Holley 4010. I'm sure that carb would've been fine had I the patience to tune it correctly and all the pieces parts to do so, but it ran so inconsistently I just didn't feel like messing with it. So, I bolted on an old Edelbrock 600, wired the choke open and it was so much easier to drive. I really wish I could drive it right now...

EDIT:

I just saw you mentioned 20-25* initial-that's a bit high, even if the engine does like the high initial, it'll be too much total timing unless you've limited it in the dizzy...I think the stock Mopar dizzy adds about 20* timing, that would put you up to 40...a bit much I believe.

Also, are you setting your timing with or without vacuum? It needs to be without vacuum advance at idle, and if connected, should be on the timed vacuum port-should be vehicle right side of the carb...left side as you're looking at it.