The engine should have domed pistons and you should be able to run what are commonly referred to as 39-48 center outlet heads. The 24 stud engines came out later in 38, so it should basically be the same as a 221 cubic inch 39 Ford. Don't throw away the stock heads - there are folks who love the early 221 iron heads - due to the tighter combustion chamber (depending on what you have on it now).
I'm not sure if anybody is currently making an aftermarket aluminum head designed for the stock studs (the shorter lower ones). You should definitely check that out first - just so you know what you're getting into. It can be a chore removing the original studs and putting in longer ones - especially if you don't have an oxy/acet torch and have not done it a few times before. Also, if you break one off . . . the whole project just got a whole lot uglier - especially if you were planning to do this with the engine in the car and are not taking the whole thing apart.
Good luck!