I must have missed the earlier posts on this conversion. I'd like to upgrade the ignition on our warmed up '61 235. I need to know what H.E.I. distributor to shop for to modify as you have detailed, and whether or not some have vacuum advance and others don't. I'd like to keep the vacuum advance. Am I looking for a later 250 H.E.I. before computer? What years do I need to look for. Seems like a much less expensive alternative than the $175.00 distributors I've seen advertised. TIA.