'64 Valiant SLANT 6 -rookie question (Chevy guy!).

The year code and engine size stamping is on the RF upper surface of the block by the coil bracket mounting boss. It starts with a letter code on the '72 and older engines and then the engine size. "R" is 1961, "S" is 1962, "T" is 1963, then they jump to "V" in 1964. After that, they started over again in the alphabet. "A" is 65, "B" is 66, etc. They didn't use "I" so "H" is 72, and "J" would be '73 but then they started using numbers for the year code right around that time. "4" is 1974, "5" is 1975, etc.
The engine size is stamped right after the year code. 17 or 170, and 22 or 225 are used over the years. ( A lot easier than Chevy huh?) They also made a 198 in the early '70's. Visually, they all look similar to the untrained eye. The '67 and earlier block only had 3 freeze plugs on the side whereas the '68 and newer used 5. Naturally, the casting numbers changed through the years and engine displacements. The '74 and older heads use plug tubes where the 13/16 wrench size, gasket type spark plugs, are recessed down in the head. The '75 and newer have external plugs with tapered seats and 5/8" wrench size. The 170 is a shorter deck engine but without a 225 sitting next to it, that might be hard to determine just by sight. I don't think I've ever seen a convertible with a 170 but I suppose it's possible. The 170 usually came on the real low option base models. The convertible was only an option on the mid and high priceline cars so they were equipped with a 225 as standard. I would think the wagon would have come with the 225 also but heck, the '64 Barracuda had a 170 option (though I 've never seen one)and it was considered a high price line car so who knows? You'd have to decode the fender tag or find a build sheet to verify it's the correct engine size. There are no VIN stampings that year so just getting the correct year engine with a date coded block before the build date of the car is going to be as close as you can get.
Have fun, Mark