The engine will take any of the Gold Star cams..65-2446 scrambles cams are a good choice for a road based engine for inlet and exhaust...
You can run standard B31/B33 valve springs etc. with those cams..
Most other components are shared with the B Series engines..
Bore and stroke are the same as a B33/Gold Star...So any of the pistons will fit from 'long conrod' B Series engines or a late DBD Gold Star...The latter is a bit lumpy, something more moderate would run more pleasantly but it's all about the type of motor you want and what you can find...8 to 8.5-1 compression ratio will run OK...
I can't remember the valve sizes off the top of my head (and they may have been altered)...However, the standard exhaust valve is quite adequate and the inlet should be at least the size of a standard B33 valve, or a little bigger if you are prepared to go to the trouble..
For a sporty type engine I'd lighten the flywheels as well...This makes a lot of difference to the performance, more so than cam and piston combinations..
If you do this and/or change the piston weight by more than 1 1/2 oz. it is advisable to have the crank/piston assembly rebalanced to a 60% balance factor...
A 30-32mm carb will do the job nicely with an inlet port opened out to match if it isn't already...
Use silicone on a NOS composite head gasket (if you can find one) or with a solid copper one if you can't to avoid oil leaks and check the head/barrel surfaces are flat...
Examine the barrel casting carefully for cracks at the front and rear, below the fins...The 500 barrels can suffer there...If it is cracked the only way to carry out a good repair is to remove the liner, weld the barrel inside and outside and then remachine it and refit the liner...
An 'outside' only repair will crack again most probably..Ian
email (option): ian@wright52.plus.com