Adding a big block never devalues a car (at least not to most people). The 348 was the only W engine to get the three two barrels often seen on top of these motors. The high horse 409 had twin four barrels to get enough cfm to meet demand.
By the way the only give away before 1962 as to whether you have a 348 or a 409 was which side of the motor the oil dip stick stuck up from the oil pan. After 192 the 409 had a big "X" cast into the front of the block because a lot of 348 motors where put in place of a 409 raced blown up and replaced under warranty with a true 409. A lot of the 409's I bought in my youth where made into a 409 by replacing the 348 oil pan with a $27 (1963 prices) 409 oil pan and a $0.90 cent decal. Most claimed 409 even if it was a 348, so I assume since yours claims to be the shorter stroke higher reving 348 I would tend to believe it.
The 348 has the same length stroke as the 327, and it shares the bore size with a BBC 396 and the SBC 400. The good thing about a W motor is that it was an eraly version of the Mark IV BBC so a396 turned down will become a stroker crank in your 348 block. You can also add a 454's 400 inch stroke crank in this engine for even more displacement (427 cubes); but once again you need to turn the crank undersized to fit in the smaller journal block. This saves money because bad 396 crank or bad 454 cranks that can not be turned 20 under (and are therefore just boat anchors) can be used in your block as a new standard crank. since you are going to be carving off nearly a three tenths of an inch (that's right the 348 crank was over a quarter inch smaller than the newer 396 454 crank journal size).