I have Paper work on an unusual Transplant from the now defunct Ray Ridge Chevrolet in Michigan.Its Rogers Chevrolet today.
A customer ordered a 1970 LS-6 Chevelle,and the dealer delivery & order papers show they yanked the LS-6,and installed an all aluminum ZL-1/LS-6 engine from the parts bin,as well as a Fiberglass front end,hood,and decklid wing.
I have three pages of docs including the part numbers from the Chevrolet Hi-po parts catalog showing there really was such an engine available back then.
I also have a letter from the owner stating the dealer told him they made 15 such 1970 chevelles.
Although not as well known as the other dealers,I feel it shows some dealerships were indeed doing similar things back then.