It's a 71-72 thing, and it's either old stock or a used one. OE part # is grp 2.410, part # 410052, switch, distributor vacuum control on intake manifold. It listed for $8.10 in 1974, but you can expect to pay several times that for an NOS one now since 442 and Hurst/Olds use it.
The three port switch will function just fine as it takes the transmission controlled spark completely out of the picture. You would then connect the DTVS to: manifold vacuum, ported vacuum and the distributor and you would have vacuum advance when it could do you some good.
Can you tell I'm not a total purist about some things?
