I believe all w-30 cars were built in Lansing M, therefore there should be an M in the VIN. You stated it started with 3448, it should continue with 70M, after the M is the sequence in which it was built which bears no evidence or authentication. So it should be: 344870M------. That does not mean it is a w-30 because it could be a 442 (non w-30) built in MI.
Is the car auto or std? If 4-spd. there should be no power brakes or AC. (note
ower brake booster could have been added)
Motor: Should have F heads with aluminum intake manifold and carb should be a 7040258 (auto) 7040256 (4spd.)
Distributor: Should be 1111979 (auto) 1111977 (4spd.)
Transmission: Auto trans TH400 should have a tag on side OW
4spd. should be a Muncie
Red inner fender wells and ram air hood (obvious but could be added)
Rear end: A w-30 car had a code TM or TO or the W-27 (aluminum carrier) had codes SV, SX or SZ. Whichever you have it must have the heavy duty rear suspension which has boxed lower control arms and upper control arm supports.
There should be a sticker in the engine compartment on top of the radiator cover that has w-30 info.
There may be something on the firewall also but I am not sure.
I got this info from various pieces of literature and people on boards like this along with personal aquaintences.
If I am wrong with any of this stuff hopefully someone will correct me but I hope this helps.
Solid paperwork and documentation seems to be what seals the deal.