If that is a 305E you can have the 2 barrel intake modified to fit a 4 barrel. If you subscribe at Jolly's GMC sight you can see pictures of manifolds that have been modified. As far as what I did.....my 305E has a fairly large mouth 2 barrel intake, so I bought a 4 down to 2 barrel adapter and bolted it right on. Works wonderfully! I have a 600 edelbrock that I bolted right onto it and Man! Let me say...she pulls quicker than I can shift! I'm still running points to with no issues. Ya gotta remember...even though they're only 305 cubic inches....the bore size was 4.250....that's fairly big. lol I think if yours is stock you'll have a 305A or B which will have the single barrel. A 305E manifold will bolt right in place and you can do the mods I did or have that manifold machined. Also another great upgrade is dual true dual exhaust. Guys commonly run 2.5 inch duals. I'll be doing that with either flowmaster 40's or 50's.
