This has to have been done before, but oddly I havent had to cross this in the past. All my big block cars were originally big block cars.

MY 65 coronet had a poly engine. I now have a 383 in the engine bay, and have a 440 Source water pump, drivers side hose mount.

I am not too concerned about the top hose, but the lower one, well, its right up against the filter. I dont even think I could get a flex hose on it. I will change radiators if I have to, but I am thinking about running the shorter oil filter then trying the flex hose.

Any other solutions besides the obvious radiator replacement?

The best thing to do would be to change the water pump housing. The 2898038 (68 318) radiator should have the right lower bung to use as I have used them in factory 383 A-Body's but had to run a short radiator cap on them. They are MUCH cheaper than the real A-Body 383 radiators.

Offset the holes in the radiator support and slide the radiator over to the drivers side 3/8 to 1/2 inch or so I have

A radiator shop can move the lower inlet over as far as it can go. I've had it done more than once.

I had the same issue on my '65 Coronet when I went to a big block. I had the radiator re-cored and the lower hose connection moved. It worked perfectly. As luck would have it, I then found an original 426 radiator and installed it. Still have the first one on a shelf.

It slips me right now, but the inlet/outlet sizing varies somewhat per Small-Block to Big Block radiator application.

True story, a friend of mine tried a freshly re-cored 26" A/C Small-Block radiator in a slightly warmed-up over stock street 383. Not an issue until the warmest of summer days when overheating was inherent. Can't recall all the fan/shroud/t-stat/pump changes he fussed with but something was deficient in the chain and I don't think he ever solved the issue.

The small-block radiator might suite you well, but it could also be a lot of effort/money invested in something that results in less than satisfactory performance and grief down the road.

As the saying goes, pay me now or pay me later...

Pic, its a bit tight in there.

Shroud would make it hard to move the radiator over, wouldn't it?

The hhr fan is attached to the radiator.

I think I had the same radiator on my old 64 Plymouth. Went to the parts store and pulled down every lower hose they had that looked close. Inlet/outlet were different sizes and it did hit the filter, but I put a sectioned hose over it to keep it from rubbing through. Your inlet looks a little longer than the one I had, but I can't remember. PM me and I can put you in contact with the new owner if you want to email him. Moving the rad will likely hit the fan. It is pretty tight.