75 valiant 225 to 440 swap help!!!

Your exhaust choices are fenderwell, which I have seen fit fine but will probably require you to run skinny tires up front as I have seen more than one conversion to fenderwells where the tires rubbed on the headers, B or C body manifolds which will require angle milling on one side for a good fit, stock A body big block manifolds which are scarce and pricey, the schumacher headers posted here which have proven to be the best bolt in with minimal frigging There are other options for headers but I have yet to see even an expensive set bolt in without a goodly amount of frigging except for schumachers... Part of the problem is quality control back then ....one 440 conversion is fairly straightforward and there is enough room for headers and on the next one the motor mount pads might be 1/2 inch different and when your are shoe horning a big block exhaust system in an A body 1/2 inch of clearance IS a BIG deal. Just because you spend 7-800 on a set of headers that are supposed to fit with minimal problems....don't count on it. i'VE lost count of the number of posts where guys spent 700 bucks for tti headers and they ran into install problems ranging from z bar clearance to the headers hitting torsion bars and steering components.The only tue bolt in ones that I know of that aren't a major frig are the schumachers. I had a 70 440 Duster and after much research and looking at big $ I got a set of manifolds off a C body had them angle milled, slapped the on and forgot about them. I never regretted it especially when I read posts by guys who had lots of burnt spark wires, their starter was captured by the headers, they leaked, rusted out, got dinged and dented easily etc. etc.. True you will lose 20-30 horsepower by running manifolds but you can make that up somewhere else in the motor or run a converter or steeper gears..........You can probably pick up a set of manifolds for 50 bucks.

If this is not to be an all out 440 and will have good street manners, the schumacher would be the best bet.The are very strong on the lower end and mid range and great on a street motor.
The price here for them and the mounts is a good deal. You can get all the radiator you need for 200 bucks, if you need a link to it send me a pm, i'll send you the link.