I don't know what happened to the originals, they're gone. Probably best to get replacements anyway. If someone has these sizes, thanks. If you know of an ARP kit that fits, even better.
I think the heads were 1/2 on the water pump pulley so the threads are 5/16-18 and the length is likely 3/4". I cannot recall the thermostat bolts but I am assuming 5/16-18 again.
Scott