HI Dan, good luck with your goals! Yes, it is possible
to gain muscle on a paleo diet. I put on 20# of muscle
over the last couple years (i'm female). I'm sure
being a male you would be able to put more on. Several
guys on this list are weight lifters.

For protein sources, well, any dead animals is good...
I make a smoothie every morning with egg white powder,
coconut milk, fruit. (I was able to get my small local
health food store to sell me 10 pounds of powdered egg
whites for $82 u.s. dollars. I think it tastes better
than any whey, though I must admit I never found one
that tasted good! Egg white powder is pretty
tasteless)

I eat meat/protein at each meal, veggies at a few
meals, and about 2-4 servings of fruit a day.
Good luck and keep us posted on your progress.
--Liz