Heat control valve spring

Having a working heat control valve is an excellent idea. The '60-'64, '65-'69, and '70-up style Slant-6 manifold heat control valve hardware is all unavailable as a new-stock or repro item; it's going to be a go-fish deal for old-stock parts, except if obtained as part of a new exhaust manifold (not necessarily a bad idea if you're going to the R&R trouble, unless your pre-'70 manifold is in unusually good condition).