Ok think big picture and work backwards. Do you want a race car? Do you want to keep the car original? (I'm guessing not due to the 440 idea) Do you really want "MAXIMUM POWER" regardless of the cost? We would all say throw a crate Hemi in it and call it done, but most people don't have 15-20 grand lying around to throw at their cars. You are at the critical stage of your build. Now is when you decide if you want to build a big block car or a small block car. Your budget comes in to play here, but ultimately you don't want to build a car you'll end up regretting later.
On the one hand, you can get good power and performance out of the 340 you have there, assuming it's in good condition. If money is a factor this is where I would concentrate my efforts. For the 5 grand budget of buying the 440 you could get a compression check of your 340. If it's good then simply a cam, lifters, springs, intake, carb and headers will wake up your engine. all for around a grand or so. Then factor in another $500 to sort out your front end problems and maybe $1500-2000 for a top notch transmission and you're well on your way to having legendary muscle car performance with the car you already have. The upside is this can all be done in stages as weekend projects so your car isn't down for any significant time. And you save $$$
Compare with my ordeal putting the 440 in my car. I had the engine and transmission already so that's a wash. I had to get new torsion bars and rear springs for a few hundred dollars, new radiator for around 500, Schumacher mounts for another hundred or so, Seek out and find a new driveshaft (904-727 probably doesn't apply to you) then mount it all up. Score proper big block pulleys, fan shroud, throttle bracket, wiring harness etc. Little stuff adds up. THEN I had to spend the same upgrade money on the engine I just suggested to you: Cam, lifters, springs, intake, carb and headers. And then my tranny went hence the same 1500-2000 to put in a properly rebuilt unit. The whole conversion took me nearly 2 months mostly because of seeking out the little things I thought I had or found out I needed later. The end result is I have a 440 in my Challenger and spent a ton of money. That didn't even include the front end rebuild to make the car driveable again.
If the appeal of a 440 is something you really want I say go for it, just be prepared for the project you're going to undertake. I suggest you either try to talk this guy down or shop around and find yourself a cheaper 440 though. I'd hate to see you blow your budget and have an engine taking up space in your garage you can't do anything with. I applaud your method of being proactive and calling people on their ads and asking questions. Keep it up. You may score an old C-body or something nice and cheap like I did.
