Those were Post, and you didn't assemble them. The Mini Lindys were the only ones to my recollection that you had to assemble, other than some larger Whacky Racers that were mail order from some cereal.
I remember getting Mini Lindys by mail, but it was probably from Kellogs. Two cars and a garage. I don't remember cars from Life, but my memory isn't the greatest either.
I had a 60s gas station that you put water in one of the pumps. One of the cars had a hole in the trunk lid that allowed you to put "gas" in it. IIRC, it had a pin on the hood like these. It pushed out a plunger on the bottom so you could drain the "gas" when you were done playing with it.