Chris;
Any particular reason why you want to go to a 396 instead of staying with a 454-based shortblock? The car isn't a numbers-matching car anymore, right?
Just tossing out some thoughts to ponder over;
As far as a more affordable set of heads goes, you could look for a late `70 or later dated set of 291's, which tend to go for about 1/2 or less of what the primo dated stuff sells for. Only thing is, the 291's have the largest intake runners of all the original closed chamber rectangle port heads, which won't help matters on a 396-based shortblock in regards to torque, throttle response & overall driveability. That's where the added cubes of a 454-based shortblock would be a welcome improvement.
If you want to port the exhaust manifolds, you might want to consider
Gessler head porting services.
A scattershield is never a bad idea, but you could probably get away with a regular 621 bellhousing and a quality 11" clutch set-up and flywheel. (A rev limiter would be a great idea as well in this regards)
re: The 163 intake--if you plan to run a 4346 (or similar) carb, leave the plenum divider intact. If you want a little extra sumthin-sumthin', you can cut the plenum divider down and run a factory L88 style vacuum secondary carb such as the 3418 which is rated at 855 cfm. I used that exact set-up on my own 496 with surprising results, which you can check out in the following link below if you're so inclined.
As far as the L78 cam goes, run the Crane blueprint cam with a set of EDM lifters and forget about it. If you feel like reading, do a search on the subject, it's been
thoroughly discussed here on numerous occasions.
Stock 3/8" fuel line is fine, and you can even use the original-style 5/16" feed lines into the float bowls, assuming you plan to run a reproduction L78 style fuel line.
My 496 ran perfect with those lines on the dyno making well over 500 HP, and the BSFC numbers even showed it to be running a little rich.
Fuel filters: See above re: my 496--it had the factory sintered bronze filters inside the float bowls during those dyno runs as well.
Not sure on a factory P/N for the L78 pump, but lots of people have had good results using a Carter street/strip mechanical pump (don't have the P/N handy to those either, but you should be able to look them up easily enough)
Hope that helps.
Eric