Vikki, my '67 did not have enough room between the firewall and a "normal" HEI. The HEI "fit", but it rubbed the firewall slightly - while sitting. Under heavy throttle, the HEI was contacting the firewall even more. It made my timing a bit inconsistent, and made the distributor wear out early.
'69s seem to have a bit more room, though, so you may not have a problem with it.
good luck, Lee
'67 Coupe, 455, pump gas, 11.46 @ 115.4, in Feb '05 HPP Shootout article
