If you want to go to an L78 configuration, for 69 they had either a 3955272 or 3969854 block with 4 bolt mains, 3856223 forged steel crank, 3/8 dimple rods, equivalent to L2242 TRW Forged pistons, 3919840 or 3964291 heads (both are closed chamber rect. port), 3933163 aluminum intake, 4346 - 780 CFM vacuum sec. Holley, 1111499 distributor, solid cam with 316*int./302*exh. and .520/.520 lift crane and compcams make a reproduction.
If you haven't spent the $$$ on the machine work, don't care about "matching numbers", don't currently have an L78, and want reliable HP there's a couple of routes to go. One would be to get a 454 from a donor and build it. "There's no replacement for displacement" and there's some good combinations (i.e. the BSE 454) that make decent reliable HP/Torque for less $. If you have the 396 and want to use it. I'd look at aftermarket items such as heads, cam, ignition and you'll end up making more streetable HP for about the same or less $.
My '69 currently has a 70 2 bolt 402 bored .060 to a 414, 063 heads with hardened seats, a CompCams XE274 cam, TRW forged L2240 pistons, 6223 steel crank, 3/8 dimple rods with ARP bolts, 750 holley, stock distributor with accel coil, stock exhaust. The rotating assy was balanced. My car is has a 4 speed and a 3.55 posi. The engine has less than 10K miles on it. It runs pretty strong and a better exhaust system would help it out a bunch. I am willing to sell the engine since I am building a matching numbers L78 for the car. It has lots of torque, is in the HP range you're looking at, is reliable, and runs good on 91 octane unleaded. It also has enough vacuum to run power brakes and vacuum headlights. If you're intested email me off line.