New to gta v and having problems swapping cars and having add on work

I wouldnt say I'm new to lspdfr I played thru gta iv. However I am new to the gta v version. I have run into a few problems which I hope some can assist me. I have downloaded open iv, added rage plugins, script hook 5, lspdfr works great in game. My problem is I have tried to switch vanilla police cars with mods and the game wont register them. The one is registers which is police2, picks it up as a civilian car. I've check patch dates 1-20 and cant find the cars in trying to add. The police cars I did find I switched the models but still wont load. I have also gone into the main directory as you could do in gta iv, and it still registers the vanilla models. My other problem is I have added two add ons, one is a fire EMS package, and the secone is a LsPD mega pack based on LAPD, i have put the files into correct folders, added it in the meta file, open iv registers they are there but gta v wont. I've done the Oiv install but none of my models will spawn. If anyone could maybe give me some pointers or help me.  I can post pictures after work. I have been so excited to play it... than I ran into these problems.  I appreciate any help or support you can give me.