Super charging my 67' 273 commando valiant

I come to this forum with humility, asking for what else I need for my lil 4 door commando. As far as required engine work, knowledge on how much boost i can and should run...(im sure itll spend a few hours on the dyno to get it right, ) and other required supporting mods i havent considered, I'm at a loss. I have searched the all knowing Google and you tubes....and can't find anything for my particular dilemma. The other guy I saw here blowing a 273 went top mount. I cant fit that under my hood. I wanna keep original body work.

Any and most advice, comments, and help is much appreciated. The continuation of this project should begin in February or march. Thank you for any time you take to give advice. I'd like to add im looking to get around a respectable 400 ponies

----this guy---


Anybody have any advice yet?