Contact at John at aircooled.net. He make sure they are all the same weight and spec. Ask Brian about the importance. If you go that way I will order them for you I get a nice discount with him.....

We're trying to find a used one that matches the current ones. Trying to keep costs down.

I pulled the heads apart tonight, and most of the valve guides are in pretty bad shape . Looks like it's in need of valve guide replacements and valve job.

Gotta do what we gotta do. PM sent.

who do you use for the machine work on the heads?
can you replace the valve guides yourself?

You can't replace them yourself unless you have the equipment unfortunately. You need some special reamers and valve seat cutters, not to mention a mill or really good drill press.
I have used David's machine shop in Houston before they do a good job

I remember back in HS in shop class we would ream the valve guides but the machine shop we used showed me the tool they used to replace the guides on my sbc heads and it was basically a large punch to knock them out and then press the new ones in

Yeah, basically you core the old ones then drive them out. You heat the heads and freeze the new guides then drive them in. Then you have to ream them to match the valves. Last, you need a new valve job since the new valve centers are probably a little off from the old ones. The most expensive tools needed are the valve seat cutters. I like to hand lap the valves too even with a fresh valve job, but just cause I'm that way, lol

Well, the heads are now back from the machine shop (Davids Machine), and I got a set of used pistons that match the ones the motor came with, so we're back on track. Also have a set of new Scat single hi-rev springs to go on the heads too. Here are some pictures!