my advice? the nice original paint and pipes warrant a good job on the frame. If you take all the easy parts off, all is left is the engine so then that is easy too. The original frame paint was not satin, it was gloss, just not a modern base coat/clear coat kind of gloss. Any gloss black single stage will look good. I recommend using a paint that is capable of bonding to bare metal such as rustoleum, especially their appliance epoxy is very good and even tougher than the standard paint. No primer! Primer is what makes paint easy to chip and scratch and when you do, the damage jumps right out at ya. Sure, there is better paint, but it is gonna cost a lot more and probably require the use of a spraygun.
Whatever you do, surface prep is key. You don't need to remove all the old paint. That o.g. stuff is still super tuff and makes a good base layer for whatever you put over it once sanded. Start sanding with 60 grit to get rid of rust pits. Be sure any old paint remnants are feather edged. Work your way up to 400 or so, no finer. Rattle can paint needs some relatively coarse toothe to grab onto. Prep all your small parts, like swingarm, brackets, etc. and you can do 'em all at once or in small batches.
