Sounds like you're on a path. I still think that a goal of 425 is going to be hard to get with your combo though.
For the TRW pistons and compression ratio just show your Dad this page from Campbell motorsports. The compression difference between a closed chamber and open chamber is almost a full point. This is HUGE and makes a big differnce. A thing to keep in mind too is these advertised numbers are average at best. Point is that you need to do some homework. Measure the deck height and cc' the heads to be sure.
To make up a full point of compression you will need to take alot off of the heads which messes with intake fit and valvetrain geometry.
http://www.campbellenterprises.com/mopar_speed_pro_trw_forged_pistons.htmThe intake manifold is a nice fit. If it's the 2 plane there is not a huge upgrade versus the stock other than weight though.
The manifolds should be mgnafluxed (I think that's the term) or magna honed or whatever. There's some companies out there that can clean up the flow by pushing a bunch of molten material through it. Not sure what it exactly is, but I remeber reading about it somewhere...
I really don't understand why this is in the restoration forum...sounds performance oriented to me.
