4 speed upgrades ?

May as well ask now so I can be looking for parts - bought a 70 340 4 speed car - building an approximate 400 hp motor. I have trans and bellhousing only - still need to collect some linkage. Starting from here - are there any recommended upgrades to the trans/clutch/flywheel/shifter I should consider ? I'll take any part recommendations. Also - wanted to keep my TTI's but looks like they're an issue with 4 speeds ? Best header ? Hook me up with 340 manifolds for a hundred bucks ? (Just kidding about the manifolds - unless...)