4 hole carb spacer for better signal, will it work?

[Mrturner1]

Hey guys, havin issues still with my new Holley 750 DP mechanical secondaries. It's on a 355 with 10.3-1 compression, RHS 170 heads, Comp 280H and has 3.73's with a mini spool and 3000 rpm stall. I'm positive this would be easier with a 650 DP but the 650 I had on the counter at the parts store got mixed up with this 750 and I didn't see the box until I already installed it. Good news is, carb will be big enough for boosted 383 later.

The issue, major stumble off idle and it even backfired out of the carb when I really stabbed it once. Right now it's got 70/75's and the shooters are .31" I think, whatever it came with. Haven't touched the shooters or pump cam, nor the PV (I think it comes with a 6.5 PV?)

It's not timing, I've tried everything with that. Backed it off, gave it more, changed springs and weights a million times. The distributor is a brand new MSD street fire and has a Moroso weight/spring/bushing kit in it. Weird thing is when I first dropped it in, my dial back timing light said 18 initial and 36 total which is great and the engine loves it. But for no reason at all a couple days later the timing light says 36 initial and it doesn't move more than a couple degrees all the way up to 4000rpm. No idea what's happening there. Got a new dial back and it showed the same. It's not runnin like there's 36 initial, it still runs just like it did when I set it all up, and it starts with ease after its warmed up and even hot, starter doesn't blink. I have a timing tape but my balancer is painted orange so I suppose I'll have to sand and acetone that and try to hit it with the timing light on "0" to be sure. I'm stumped there, could it be bushings or something like that? Wouldn't it have symptoms of 36 degrees initial?

Anyway, original question was this. I have an open 1" phenolic spacer, would a 4 hole give it a better signal since it may be too much carb for this engine and setup? Help with the other issues is also greatly appreciated. This project is very close to being driveable! Thanks guys