Car-Part.com lists warrantied motors for Tundras (same basic thing if you are looking to be cheap) for under $2500 with warranty....just sayin.
I get where the OP is coming from. I guess from working on cars my whole life I have a different outlook. The welds don't look that terrible, its already a rusty 9 year old used SUV, and throwing Lexus dealer priced new parts is throwing good money after bad. If it was some super pristine late model with 20k miles a different path would make more sense.
Common sense says toss it on a frame machine, make sure its straight enough to be aligned properly, let a good frame guy get a look at it. If he says its all good, toss a used motor in it and drive it. Lots of cars on the road that have been damaged much worse and fixed much worse.
Is there evidence of body damage as well (repaint, missing or damaged panels or trim, body lines don't line up) or was this "ran it over road debris" situation?
Hell if you were closer I would love to buy it, fix it, and let the wifey drive it.