I Need a Slant 6 Ventura county

Welcome from NorCal. 1965 engines have 3 core ("freeze") plugs. Later engines (70's?) have 5 core plugs all in a line. I attach a chart of casting numbers. I thought the 3-core slant in my 64 was original, but found it isn't (casting 2463430-8 means 1966). I couldn't interpret the stamp on mine behind the alternator bracket (V 22 8 14). I attach other info for a rebuild.

It is fairly easy to remove the head with the block in the car. I even did that on my 69 Dart long ago when still a dumF kid. I would do that if a head gasket leak is your only and true problem. I would spend some time diagnosing first. Head gasket leaks are fairly rare in these cast iron heads. I think they are more likely from corrosion than anything else. Most commonly, it would cause 2 adjacent cylinders to show low compression. If you do remove the head, have hardened valve seats installed on the exhaust, or use a later head with hardened seats. Much info searching here or on www.slantsix.org.

If you do install a later engine, after a certain year (1968?), the hole in the crankshaft for the torque converter's snout (if auto) is bigger, so you need a special ring to fill the gap. If not, your transmission will probably self-destruct. Charrlie_S sells the ring for $20. I would keep your 65 tranny (if auto) since that is 1-year only, with the cable-shift and standard pattern. It would be a lot of research and thinking to change it. It is a neat tranny anyway. Did you know you can push start those cars? Not possible after 1965 (no rear pump).