Kanters or egge obsolete engine parts.
With these engines, there is no reasonably priced rebuild kit or parts for the engine.
I can wholeheartedly recommend Terrill Machine in Texas. I got all my engine parts from them for a partial in 2010 and for a full rebuild last summer.
They are reasonable, have name brand parts, and also are a wholesale supplier to others who sell to the antique car trade.
Their ad is in Hemmings in the Cadillac section.
Feltz Terrill is the owner and very knowledgeable about Cadillac engines.
They do business the old fashioned way, over the phone, talking to a real live human being who actually knows what they are talking about.
If you call, you could mention my name.
Here is a kit for 2500 USD. I guess it will take care of the problem for you. Not cheap though.
I do think someone posted here or on main CLC forum about problems with the Kanter set. At the moment I think I would stay away from Kanter.
I can't see you and Kanter doing too much business in the future. I know where you're coming from too, I recently had issues with a mob here doing stuff on my ride on lawn mower.
Big blow up, then I shut the account. Pretty bad when people can't/won't do whet they promise.
Google about the hardened valve seats mate, lots of info on them.
When I rebuilt the bottom end of my engine (heads previously rebuilt), I used the Kanter Deluxe rebuild kit and had zero issues, other than the fact that the kit did not include the rear of engine cam plug. I found you can simply punch them out of the back with PVC pipe, and reuse or get them really cheap from Rock Auto. Just to note the Rock Auto cam plugs are the cup type and not the flat slightly concave original type.
I have heard of others having issues with Kanter Products, and am neither trying to defend nor excuse any issues others may have had with them, but I have 4000+ miles on my engine rebuild with the Kanter engine kit and so far so good, and would be remiss to not offer my positive experience with their product. I have also heard good things about Egge and Terrill over the years. As pointed out a complete rebuild kit is not going to be cheap!
Also one thought. If I would rebuild my engine (not necessary right now) I would look into the possibility of converting to hardened valve seats. Not sure its possible and if parts available or how its done though.
Would love to read and see a full blog on a 63/64 Cadillac engine rebuild project with pictures taking us through each step.