How many assemble their engines

My family has always raced since before I was even born. I grew up learning how to assemble chevy 350's. I love it. The issue is, that's all we really did. I've never built a transmission, or a rear end. We usually had different shops do that. We'd have out blocks machined, and the shop that machined the heads usually put the valves / springs / guides and ground seats for us. I have a ton of experience in "assembling" the engine, but I feel like I missed out on a lot of experience by having different shops do most of the work. One of these days, when financials allow, I'd like to try my hand at rebuilding a transmission. Soon enough I'm gonna try my hand at a rear end lol