i'm not a huge fan of measuring CHT personally but when you first get into tuning its a nice thing to have. Usually by the time your first trail tech battery dies or breaks you know enough to not need one, haha.
to answer the OP's question, yeah 45 or 50 is pretty do-able on a basic reliable build.
#1 replace the crank and all bearings/ seals in that motor. hard to tell from the pic but that crank looks rusty like it had water in the bottom end at some point
#2 echoing what others have said a pretty basic 70cc piston port kit will be the easiest best way to go, lots to choose from but the kstar and metrakit are probably the two most fool proof choices at a good price point. The TCCD are a little more touchy and I've never built the super cheap airsal, but i've heard folks having odd issues with them. The malossi 62 is really really nice and if money isn't an issue that is probably the best one out there of all of them. Good torque and practically tunes itself.
#3 complete the setup with carb and pipe, once again lots of good choices but certain combos compliment themselves. the pipe will have as much if not more to do with the way the bike rides than the kit. If you're keeping it simple and going for realistic performance expectations the proma GP is a great choice for low end, proma circuit gets you a little more mids and tecno estoril probably best all around with some size complications.
a good way to get setup for the first time is find someone who knows what they are doing and straight up copy their setup even down to the jet. From there you can fine tune but for these simple setups its not too hard to go right to a running bike by just doing a pure cookie cutter of a good setup.