68 cuda automatic to manual conversion

ON THE STREET,
With that much engine, I would think the auto is a better match. Even if just a 727 and hiway gears.
But if you want to row gears, that's your preference. As it was mine.
But think about it; unless you have deeeep rear gears, or are short-shifting, there will not be a lot of rowing going on;
Cuz
65mph at the Top of Second, is about ;
5000 with 3.23s; 5500 with 3.55s; 5770 with 3.73s; 6050 with 3.91s; 6350 with 4.10s.
If you shift into Third early, you will drop a bunch of rpm, especially so with street-friendly gears.
Now, as for me
I like to shift at 2800, cuz my lil 367 is just purring real nice there.
So; at 2800 with 3.55s, the mph in each gear is about; 20/33/45/63
So if you want to row gears, on the street, you gotta short-shift.
The other thing is this;
How slow do you want to drive? and how slow will your 408 idle at?
If 700 is your minimum in-gear idle speed,
then with a Regular A833 (2.66 low gear), this is about;
6.5mph w/3.23s; 5.95 w/3.55s; 5.66 w/3.73s; 5.4 w/3.91s; 5.15 w/4.10s; 4.9 w/4.30s; sooooo
If you want to parade it, yur kindof outta luck. Sure you can ride the clutch, but for how long?

BTW
As to a 4-speed; I believe that I have everything you need, except the floor hump and the Back-up switch-wiring, but no under-dash reverse lite. I'd have to scrounge around to find it all.