There is no front/rear. For master cylinder all you need to worry about is the caliper piston sizes and pedal ratio. The master cylinder (MC) is only there to provide volume for the calipers.
The brake bias comes from your prop valve and rotor/caliper sizing.
You can use the largest MC you can find, there is no such think as too big, just to small. The above are the minimum you will need to even be close to decent.
The larger the bore of the MC the less stroke you will need, but the softer the pedal will be. If you can live with not so good pedal feel then get a 26.99mm MC, which is what is used on most large trucks (Like Ford F-150).
Here is how to calculate mechanical advantage:
Area of MC * pedal ratio = M
Area of front piston= N
ME= M/N = larger is less effort
25.4mm (1 inch) MC gets you close to a 1:1 so for every 100lbs at the pedal you get a 100 pounds at the caliper.
Your racer only weighs 1500 pounds you don't need much.