Biased but I'd go Big Block. Geometry is fairly different from what I understand -- haven't looked at Wabi's geo charts recently but they're much less tracky I think, if that's a factor for you. As for where you could find a fifth gen for sale, either used market or you could try asking any local All-City dealers. There's a chance they might have some old stock or can contact AC directly to see if they have any floating around.