Rob,

Don't discount the BW35 if you want just a cheap, around-town beater 164. I am very satisfied with my slushbox in all respects, though it is a late one. Mated to B20F/K-Jet/K cam/4.10:1 rear running 165/70s. 23mpg.

Yes, rebuilding them is outrageous: $750-1200, varies greatly.

Plenty good (read usable) BW35s kicking around still, in & out of DOZENS of makes. Shouldn't be hard to find one if you ask around, people aren't thinking they're worth selling. Buy a bunch and just keep putting them in when & if you kill them, they don't weigh a whole lot.

That being said, the high-compression B30s tend to kill them fast, so year is an important factor if you want to do BW35.

Also, if you were to do an M410 swap I think you'll have to dig up a crossmember for the OD to rest on, but this might be shared with 140 series. To get that you might end up having to buy more stuff than you really need to make this a go-car.

A late BW35 164 might have the coveted 3.91 rear though. Either way, if the car runs and isn't crunchy with rust and accident damage; totally worth picking up.

--
1966 122s, 1970 142s, 1974 142e... Blue is beautiful