Welcome to CHR!

We’re an odd lot of mostly old hot rodders with a smattering of youngsters here that keep us on our toes. The well of information is deep and I continue to learn and enjoy the posts.

I would not alter the firewall and I think Ken is pointing you in the correct direction, re; a smaller diameter distributor. I have no experience with Procomp Electronics but my insides are having a tough time with a $78 distributor. It is the size you want, but the one review is not good and I would shy away from it. I have used the Mallory Unilite on multiple occasions and had very good success – however, it is north of $400! https://www.holley.com/products/igni.../parts/3748201

Another company that I have used on a few builds and highly recommend is Davis Unified Ignition (D.U.I). They make a really good product and have a kit built for tri-power and blower setups where firewall clearances are an issue - Chevrolet V8 Tri-Power Ignition System https://performancedistributors.com/...nition-system/

I checked their site and they are 8-10 weeks out on delivery of this product but if you can wait, it’s a hundred bucks less than the Mallory unit. It does require an external coil – come with the kit. They're located in Memphis and you could call them (901) 396-5782 and tell them about your build. They're nice folks and may have an another solution that will ship right away. I know from experience that if you ever have issues with their componnets they are super patient and helpful.

Hope this helps a bit – let us know what you decide.

Regards,
Glenn