Hey all - this is probably as easy as it gets, but I can't get a replacement vehicle to work.  It's the Blaine County Sheriff car from the site here.  The readme says:  Install Location: x64e vehicles.rpf AND patchday3ng.  So, in OpenIV, I've placed these files into mods/x64e.rpf/levels/gtav/vehicles.rpf AND mods/update/x64/dlcpacks/patchday3ng/dlc.rpf/x64/levels/gta5/vehicles.rpf.  Are these the correct paths?

I did previously install a BxBugs CVPI LASD 1.4, which I installed with a package installer through OpenIV, and in game, that's the only custom police car that appears.  I think that both these cars may be headed for the sheriff slot, so I was expecting that the Blaine County car may have overwritten the other one, but only the BxBugs car is showing up still.  Any ideas?

Many, many thanks all!

So the plot thickens!  Just to experiment I renamed all the Blaine County files, which were originally sheriff.ytd, etc. to the police3.ytd, etc, and put the files in the same two locations above, still getting the stock interceptor.  Any ideas?

Thanks again, all.

Well mystery solved...after a lot more digging I saw that Open IV has a search function, in which I discovered a *third* vehicles.rpf in patchday5, which contained only three or so vehicles, and one of them was the other car that did work.  So - I put the new car in there and it's working fine.  I put another one in as well, ignoring the two vehicles.rpf files that the readme said to use!  Oh well - at least it works!