Getting back to it and straightening a bent chassis

[Speedex750]

An inch and a half is a long way out, presumably the spring mount is similarly canted and the car would ride oddly. Perhaps, if you have welded a new top right down the rail you have to accept that it's scrap and get a new rail or chassis. This was usually a problem when folk boxed in the bottom of the rails but even then 1/2" to 1" was the normal bend. If you are rather wedded to this particular rail you could either cut the repair off and have another more considered, compensated, go at stitching a new plate in. Alternatively you could heat it right through by embedding it in a fire and levering it against two very fixed solid objects while checking that the channel rail width doesn't open up or close too much.

I hope you're successful!

Dave