When I did the LS swap on my truck, I wire brushed and painted the front half of frame while the drivetrain was out. I used VHT Chassis Paint from the parts store. It looked great and has held up very well after 4yrs/50k miles. A simple wipe down and it looks nearly as good as it did when it was fresh. The only thing I've found that really hurts it is brake clean, I've hit the frame here and there doing other jobs and it streaks it/tries to wash it off. But I just scuff it with a scotchbrite pad and respray that area, good as new
This was freshly done. I used pieces of cardboard boxes set on top of the frame rails to keep the paint off the bottom side of the cab and did small sections at a time
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And here's a year or so ago during the T56 swap. There was ~30k miles on it at this point, you can see how nasty dirty it is. But a good wipe down and it looks near cherry, I'm very impressed with this stuff
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