Based on budgetary constrants:1 Be sure everything you reuse is A1 shape such as rocker arms and shafts, valve stems and seats etc. It need not be new but is should be within the wear limits in the shop manual. Get a shop manual and talk with machine shop operators to be sure they know about Yblocks specifically. This is IMPORTANT.
2 Talk to a local cam grinder, for instance Berry Cams in Minnisota or Clay Smith now located in Maryland. Describe your application to them and get a co ordinated reground cam kit from them. Be sure they supply compatable lifters and slightly better valve springs. You don't mention your trany but guessing a Fordo that will not be changed you are somewhat limited in cam selection but there is help there. Don't go too wild.
3 Replace the solid 1/4" pushrods with tubular ones.
4 Port the iron intake manifold as discussed here several times, you should be able to find a thread about how to do it.
5 Get the 57 distributor recurved to give about 30deg centrifugal advance set static timing set the static timing at about 10 deg. Get new distributor wires. Most people are now using an electronic trigger like a pertronix.
6 Compression is already low in these engines and the replacement head gaskets are thicker than the steel shim variety the engines came with. Head milling removing about .040" is helpful and with the new head gaskets should not require machining the intake surfaces. Mill more if you can afford it.
7 Use the '57 ex manifolds and be sure you have high flow mufflers, ie not Cherry Bombs etc which actually restrict flow worse than stock.
HP might be in the range of 240 to 270 Torque maybe up to 300 ftlb, RPM up to 5500 no sweat.