75 psi is 55 to 60 psi too much. I'm surprised you didn't push out the head gaskets, too.
The system is designed for 20 lbs or so. Think radiator cap. They are rated at or up to 20 psi.
Snail gaskets do rot out, eventually. This is normal. 75 psi could push them out.
A gate valve is infinitely more adjustable than a ball valve. I shoot for 140-150* at idle. and 125-130* at cruise.
Berkeley used to have a fitting in the pump to restrict the flow. Yours may or may not have one. Gate valve is better, IMHO.
Pressure regulators complicate a simple setup, and are not as reliable, again, opinion.
Save your money for gas

Dan'l