Surya's mod is for VC, we're talking about GTA3 here. Alpha-channels are a bit different, if I remember correctly.
It doesn't make any difference though? VC cars can be used in III with no problems if you change the TXD format, but they won't be as reflective, thus being a little bit unfitting. Editing the materials in 3Ds Max fixes this. I never encountered any issues with the alpha channels when editing the cars and even when using them directly from the game, with the changed TXD format. It's useless to mention stuff like "ITS GTA 3 NOT VC" when you can get them in the game with some tweaks.
Who cares if Surya's mod is for VC? They are converted from mobile and they work ingame, so they should work in III aswell. Albeit I don't reccomend messing with them in Max if you're not ready for material and hierarchy editing, because they seem to be screwed for some reason (every material having the 1.0 specular value yet some of them aren't supossed to). Not only this, but the hierarchy is messed up aswell (every dummy and model is linked to the chassis_dummy, minus the car dummy).
Between Majestic's cars and Surya's mobile converted ones, I'd choose material editing and hierarchy reorganizing (mobile ones) over smoothing blocky models (majestic ones), but they aren't a bad choice either.