Nice work! Are those the OEM valve seats and sizes? It ought to breathe pretty well, ya?This thing's gonna have a throttle response like a motorcycle
I started looking for the anvil in here... What is the best approach to get there? Small mill (G0704)
Start with two or four flute end mill cutter and follow with face mill? Or can I use just the face mill to get it to size?
I think cutting the top of the track is a poor idea. Presumably, that area is work hardened, from tough service, so will hold up to hammering well and be difficult to cut with light equipment. If you want/need a flat surface to beat on, two options. Make a cradle to hold the track inverted or get a piece of plate stock.