The easiest way to ship that I've found is USPS flat rate boxes. If you can get an item in a flat rate box, it makes the shipping costs very very simple. You can get right on their website (
https://reg.usps.com) to buy labels. Stick the label to the box and drop it at the post office. Doesn't get much simpler than that. They have quite a few different sized boxes as well, and they will deliver boxes to your house for free if you order them through the website.
If you have things that are larger than the flat rate boxes, things get more complicated. At that point you need to find a box it'll fit in, or make one, and start getting prices. You can get price quotes from most of the big shippers (USPS, UPS, FedEx, etc.) on their websites. You can usually buy the postage there as well.
For really large or heavy items, freight becomes your only real option. FedEx and UPS both do freight, but it's usually crazy expensive. Fastenal (yes, the bolt place) will do freight. You have to completely crate up the item you want to ship and deliver it to one of their stores, then they will ship it to another store. The details and costs are on their website. Forward Air (think that's it) is another one. It's again a terminal to terminal type deal. Greyhound (the bus company) will also do larger stuff, but I've seen some horror stories of things being really beat up going through them. There are others for freight as well, just depends on what you're trying to ship and from where and to.
If you have any specific items, let us know and we can start pointing you in the right direction.
If all else fails, specify local pickup only.
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1983 J-10 - 4.6L(MPFI)/CS130D/Hydroboost/NV3550/D300/44/44/3.54/Disc-Disc/32s/42 gallon 'burb tank