Amen on a lot of that Old Sub! Just a couple of months ago I learned the almost hard way about the brakes. I have a C-10, probably much lighter than your Sub. I took it to Portland and back and came up over a hill at 75mph when low and behold, in front of me was stalled traffic. In any of my other vehicles, it wouldn't have been a problem. I hit the brakes and I was obviously not slowing down fast enough. I stepped on the pedal harder and the brakes locked up and put me sideways. I pumped the brakes, rode it out, and missed the retaining wall by an inch and the truck in front of me by less than a foot. My wife was with me me and we both just about had to clean our underwear.
I'm upgrading to a 261 in progress. Before the swap, I'm adding discs. I don't mind the manual steering and will keep that the same.
Last but not least, I believe that more important than the motor is the tranny you use and radial tires. A low geared rear like you have with an O.D tranny or a T-5 plus radials will blow your mind. By the time I had installed my O.D. and switched to radials, I had already bought my 261 block and started the build. I wouldn't have if I knew what a big difference just the O.D. and tires made. As far as suspension, I have a 62 w/ IFS and rear coils so I'm happy with that but I would definately want to upgrade if I had '52 suspension. Do your research, many, many options.
OK Just one more thing. Building an I6 is not cheap. You could add a crate 350 and even with all the chassis mods, would still spend less than properly building an inline 6 that will swap right in. That being said, I would still go for a 6, but it's your wallet.
