If you want great fit and finish in a model, go with Tamiya, great quality but twice the price of a Revell and 3 times an AMT. However you are for the most part limited to Imports. As for wheels check out plastic-models.com I think. Its a branch of tower hobbies. Or search for pegasus hobbies, they have some of the most commonly used after market wheels. As for lowering. Dry fit everything first and see how the suspension sits. Sometimes it is necessary to remove and re-align a-arms, scratchbuild your own, or sometimes its as easy as shortening the coil springs and or shocks and bending the a-arms up or down. There are lots of ways. If you are building a shelf model, then removing suspension parts gets the job done. If you need or want some advice hints or tips feel free to pm me. Not to hi jack the thread but here is a link to my photobucket with all of my models
http://s12.photobucket.com/albums/a218/black2002ls/
also a great forum to visit is at automotive forums in the auto art section we have a whole forum dedicated to plastic models. Some of the finest builders in the world over there a great FAQ and a wealth of knowledge and desire to help others!