Small block hei distributors

Im currently running an msd pro billet distributor in my 360. It does not have vacuum advance. Getting a whopping 8mpg out of it.

So im looking at my options. Before putting the wideband on and messing with the carb, im getting timing sorted.

To that end, im looking at the cheap hei distributors. Theres two versions. A lage cap and a small cap.
Large cap appears to be able to accept the stock gm replacement parts. Does it ise the same internals as a large cap gm hei? Such as the advance weight, springs and bushings? Will it clear a duster firewall?

The small cap is much tougher. Cant figure out what cap and rotor it uses, etc. What about advance weights and springs?

Im trying to get a distributor as easy to tine as the msd, with vacuum advance and a non msd price tag
dusterbd13, I'm running a large cap GM HEI in my 64 Valiant small block, as far as I know the it is in stock configuration; it is a tight fit, been in for 4 years now, no issues, I always carry a spare module in glovebox.