I have a 1970 40 with a 350 out of a 92 Buick. Sniff test was all that was needed and passed 3 years in a row, first two years standard plates and now I have collector plates. I do have the original vin plate on the truck. No cats required in 70,
. I am injected and live in Douglas county.
I would say go for it if your putting a newer motor in your rig, you should not have any issues.