I agree with TUTS 59, the older engines had a wide gap between the pan and timing cover, I don't know when the change occurred. I built a 383 with a mid 70's block and that pan gasket with no issue. You could use a newer pan and front cover with that gasket or original style pan and front cover with the original style front seal. Any small block Chevy pan will fit the engine as long as it clears the suspension.

1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy