Firearms and value are seldom like cars and their value when it comes to older specimens (antiques) in good condition. A 1974 Dodge Challenger in good condition is worth far more comparatively than a 1974 500 is to their current equivalents. Meaning, a high-production car from 1974 that has lasted this long is a rarity and is a technical "curiosity" compared to new tech while a 1974 gun is almost
expected to still be running with proper care so is less scarce AND it functions similarly to current offerings. There has been little tech advancement if you know what I mean. You pull trigger, firing pin hits primer, cartridge fires... So in utilitarian terms, a 1974 gun that goes bang and looks good is not usually worth more than a similar 2021 gun that also goes bang and looks good.
I am not a collector so I can not tell you if your 500CT is "special" and/or valuable. What I can tell you is you could probably get a Hogue shorty stock and turn your 500 into the Bantam you desire. I don't know what barrel you have so that could be a factor to you if the 88 has a more desirable barrel length or style.
PS: upon further consideration, I have determined that you should keep the 500 AND buy the 88.
Dilemma solved! Your welcome!