Thanks to the new 25th anniversary update, the glorious counter-strike brush entity known as FUNC_VEHICLE is now available in Half-Life.
I have seedees tutorial on my site here for it: https://the303.org/tutorials/gold_func_vehicle.htm
If anyone has made an HLDM map with func_vehicle let me know, id want to play sometime
Current issues so far ive noticed:
-acceleration sounds seem to not play properly
-idle sounds seem to be very delayed