What Chvyman said about the resistor wire. After that, if you want to spring for an MSD 6A/AL ignition, it basically removes all the electronic guts from the HEI removing most of the shortcomings of that system. I had this on my 68 Camaro and it was flawless. Another point to consider is you may need to clearance the firewall to fit the cap. I used a 2X4 and sledge to move the firewall back about 1/4".
1968 Chevrolet Camaro getting an LS-1/T56 transplant
2012 CRT 6 SP ZL-1