That turned out beautifully! The wheels from the mid 70s get a little hairy towards the end of the BBQK lid vent era especially when the bowl vents were changed to the large tabs, there have been examples of both the thin whitewall plastics and the modern style like yours. By the "engraved" WEBER elongated "b" vents the wheels should have been switched over fully. Definitely in use by 1977, however speculation points to 1975 at the earliest appearance. Metals were long gone by then.