Its best to start with a head 78 or newer.
Need to mill the head at least .070" to get the cc's back to close to 52 rather than 60 cc's.
Use Victor head gasket which is .044" thickness crushed. Carquest has them.
The intake log will have to have the low spots filled in by brazing so when the single barrel mount is milled off you will have sufficient surface for the seal to a custom made holley 2 barrel adapter.
You can use a 7448-350 holley & rejet to 59-60 jets
I use a 4412-500 holley with custom installed annular nozzles for better response & power.
My engine had flat top pistons which bring the compression ratio to 10.4-1. Camshaft during the chassis dyno test was a 274 degree camshaft with 1.6 roller rocker arms.
The little engine put out 145 HP at the rear wheel with a C-4 trans
, so the engine was putting out about 180 flywheel power.
Cost wise its cheaper to install a V-8, but the six does get good fuel miliage. Bill