I think all of the vendors will get complaints of service now and then, but most are reasonable. My experience is that Jim Carter ships everything for the exact shipping costs, but will ship stuff at different times and charge you several times for shipping instead of all at once. You may be able to request that they hold until all items are available for one shipment.
LMC has always been quick to get the parts to me.
Classic Parts I have no memorable thought on one way or the other.
One of the truck freak members here in the forum does classic truck parts too. I ordered a windshield and had it shipped to an address in Texas. He called back to check on the order and made sure that it was delivered in good shape. Outstanding customer service. Who the heck was that?