Wrong distributor for 69 318?

Hey everyone. I've got a weird distributor issue that took me way too long to diagnose (since I kept thinking it was fuel - classic mistake...)

This is a recently rebuilt 318 original to my '69 Barracuda. Pretty much stock except for dual exhaust and 4 barrel intake/carb.

My (probably original) distributor's housing was broken, so I replaced it with this one:

https://www.oreillyauto.com/detail/...95368caf/wai-global-distributor-new/wair/ch05

I know for a fact that my timing marks are correct, timing gear is good, firing order is correct.
My vacuum advance is plugged in to the ported vacuum port on the Edelbrock, not manifold.

I've set my timing to 13* BTDC at 700 rpm and have a great idle out of it. Timing all in is 36* at ~3000rpm. This was all timed with the vacuum advance disconnected. However, light-moderate throttle is almost undrivable with this setup, popping and stuttering like crazy no matter my AFR (I played around with everything from 11.5-14.5 when I thought it was fuel). If I lay into it 80%+ throttle, the stuttering goes away.

I tried unplugging the vacuum advance and driving it, and it drives fine that way. No popping or anything. It seems like the vacuum advance on my distributor is somehow too aggressive - maybe the part I got was a "generic" SBM distributor that doesn't work well with my '69?