How much power do engine mods yield?

Thanks for all the info guys! Torque is indeed what I am after...

The car will be used mostly as a commuter on 55mph roads with city driving making up 50% of the trip. Previously I used a 1961 Falcon as my commuter but that 144 inline was a dog... really got tired of people thinking I was an old fart poking along and cutting me off!

Interesting comment on keeping the auto tranny... would not have guessed that.

I always wondered about the rationale of drivers who aggressively cut me off to not be behind my 45 year old Valiant...cuz now they're in front of my 45 year old brakes...