I'm sorta in your same boat - 452 heads, stock valves. I just kinda went for it, no templates, first time I've ever ported anything. I read an older post on this topic that said the templates don't address what's actually needed which is the short side.

For the PR pinch I didn't go nuts with metal removal just more smoothing it where the intake runner meets the bowl. My concern is that I went too far and took too much away from under the valve seat. I lapped a valve in and I still have a decent margin. The margin looks chewed up in this pic but it's really not. The valve faces are pitted anyway.

I have no expectations for these I did it more as an exercise just to see if I could do it. I promised myself not to spend any money on these heads beyond new valve stem seals. Thankfully no metal in my eye yet.