Unibody sleeving

I have an '88 300zx that I was planning a 5.3L V8 swap for, but it has some structural rust. The "frame" (its unibody. If anyone knows the proper term, please let me know) rail on the passenger side near the firewall is rusted away. I've been told to try coating the rust in a converter and building a sleeve around it to reinforce the weakened structure, but I don't know if this is a good idea. I see how this could reinforce the rusted area, but it seems as if there could be some unintended consequences due to the thicker material causing different amounts of flex than the stock material. I really don't want to abandon the project, as I've purchased an engine and transmission for the car, but if sleeving is a bad idea, I'd rather know than build a sleeve that will eventually destroy the car.

I think if you throw a V8 in the car, you have other reasons to worry about flex and structural rigidity. It seems like you'd want to sleeve more than just around the rust, but maybe do entire subframe connectors tieing the front subframe to the rear subframe on both sides of the car. If you throw that big of an engine up front, you're already going to upset the balance and handling of the original car I would expect. I would think you're doing this project more for straight line performance rather than handling anyway.

-Rod

I had been reading about repairing the rusted section and someone mentioned flex rates causing cracks to form if the unibody was repaired with a thicker material than stock. I didn't even think about the increased torque from the v8 flexing the car to begin with (I should really stay away from the internet when I'm drinking...). Thanks.