Add seat to trunk area of K5?

[Electricduane]

I was inspired by Huggerorangeblood's thread about adding a center console/jump seat from a 2015 Silverado (I think) to his K5.

Has anyone added a second rear seat to the trunk area of a K5? It would then seat 6.

Obviously a rear seat from a 73-91 K5 would work. The second rear seat of 73-91 suburbans are extremely similar, if not identical. Later model Suburban seats would likely work as well, tho I have not tested that.

Once you get the seat, you would need to figure out how to attach it to the trunk floor. Essentially remove the gas tank and reinforce the underside with some sheetmetal or very large washers. Sandwich the trunk floor with sheetmetal/washers and bolt the seat in. Similarly use sheetmetal/washers to bolt in aftermarket seatbelt mounts.

Question 1: is the trunk floor metal too thin to weld the sheetmetal/washers to the underside? Or is it good enough/better idea to just sandwich the trunk floor and possibly seal up the sheet metal/washers with some silicone in order to avoid/limit moisture and rust.

Q2: After you're done, is what you've created safe? "Crashworthiness" is the legal term. If kids are riding in the 2nd backseat and you get rear-ended, is the vehicle reasonably safe? Obvious comparison would be riding in a Yugo or some other tiny/flimsy car.

Q3: After you're done, is what you've created street-legal? Can you get pulled over/get a ticket for essentially creating passenger seats in the trunk area of a vehicle (obviously not OEM-designed for passengers)? Since I live in California, I strongly suspect the answer is "yes" (by default), but I wanted to check with you smart people.

Thanks!!