You will need .030" rings. 4.025-4.027 would be about correct for a piston in a .030" bore. Most of the single valve slot pistons were forged. If you would like to know the lift on that cam.. You can measure it with the vernier. First measure the lobe on the side. (lowest reading, base circle), then measure it top of lobe to base circle. Subtract base circle from top of lobe figure. Then multiply the result by 1.5 (rocker ratio) and you will get the lift figure.