whatever you do, if you replace the pipes let me know. i just got a '75 550 over the summer and my pipes were in rough shape. I'd like to keep mine all stock, so if you're looking to sell i call dibs!
looks good though - honestly it's a hard decision. a "factory" color will run you ~$150 if you want to spray it yourself - there's a thread on here fora guy who sells the vintage honda colors in spray cans that would work well. then you'll need new stickers for the tank - ~$80. a new side cover will run you about $40.
i've already put in about 100 hours on my restore, but mine looked way rustier than yours (i don't see rust on yours? may be photo quality). taking everything apart, sandblasting it, repainting, cleaning, polishing, blah blah blah.
it would be quicker and probably cheaper in the end to cafe' it out.
if you're looking to resell, near-mint stock bikes around here (i'm from OH) of the 550/750 go for around $2000, but i'm talking NEAR MINT. no dents, perfect chrome, no leaks, all tuned up, and low miles.
there was a guy right over the border in MI selling a MINTY orange 550 for $2300 a few months ago, but that thing looked like he just pulled it out of the crate.
to get yours back to that shape you won't ever get your $$ out of it if you're looking to flip it.