Re: 5 spd options....
I think you have a nice combo.
If you run a 3:42 gear and or 3:55 gear with a 27" to 28" rear tire, you will have a 2500 to 3000 rpm cruise at 60 mph. I had a powerglide with a 3:08 and it cruised at about the same. I dont know why that was, but I thought I would mention that.
If you tune your engine with a good timing curve and or lock it out and use manifold vacuum you will basically eliminate low speed bucking at around 10 to 15 mph. Like 36* of lock out timing with say 12* of vacuum at cruise.
The milder the cam the better to get that 400 horse. If it is rowdy you still will have to tune, tune, and tune to get where you need to be.
That is only concern I see there.
If you want the rpms down even more at high speed cruise, just make sure the cruise rpm is still within the powerband of the cam and the cam does not start to lope at cruise.
You do have a choice of overdrive with what you have already said or another transmission, or maybe a gear vendor unit.
If you just drive the car on Saturday and Sunday, I dont see the extra money spent on that overdrive.
67 chevelle malibu / SS/ custom
Currently undergoing a metal work to remove all rust, if I ever get there.
Cant decide on prostreet or cruiser with a 4 speed.