I have exactly the same engine in my Jeep. It is a 1974 marine engine that i got free from a mechanic friend that has a boat shop.

I had the low end rebuilt with off the counter parts from any autoparts
stores. I used a 1978 flywheel and clutch parts bolted to an NP435/205.

I then added an Edelbrock performer top end kit, 670 truck avenger, shorty headers and HEI distributor. Happy with the results i estimate 350 HP and 400 lbs.

All parts are interchangable with any 351w.

GH