fusible link smoking

Your alternator allows either charging option. Best path depends on what engine harness you will use. Since appears you plan to use the later 1971+ electronic ignition (have 4-pin ECU box), you should get a harness for a say 1971 to 1973 small block (1974 started some new stuff). Such harness would also have connectors for the later 1970+ Vreg w/ triangle connector. You wouldn't want to use your old mechanical Vreg w/ electronic ignition anyway.

If for some reason, you want the old-style charging, you can get an electronic Vreg that looks and works like the old box. Just ground one field terminal w/ a jumper to use that.

Personally, I would use a GM HEI ECU and lose the ballast resistor, but that requires more custom wiring. If you price Year One engine harnesses (from M+H), you might find custom wiring smart.