That truly is a "classic" hot rod (the original hot rods) staple.
Actually, that is quite similar to something I am thinking of to integrate tartan into my interior too. Only using wool fabric.
If you, your wife, or a good friends can sew, what about getting a CHEAP seat cover set and sew the blankets to the covers. That way, they won't fall off, esp. on the front buckets.
They worked so well on hot rods thanks to the simple bench seats and little shaping.
Anyways, I like it!