Engine mounts aren't difficult. There are a few options. A few adapter companies offer swap mounts, Advance Adapters and L&L Products to name a couple. In the past people have used fox body Mustang mounts IIRC.
IMO the cleanest and easiest engine mount option is 4.0L mounts and adapter plates. You can buy 4.0L mounts that bolt to your I-beam ranger fframe, should directly bolt in palce of the 2.9L mounts. There are a few sources to buy plates or you can make your own. I'd recommend Rick's Rangers as a good place to buy with quality products.
Forget that engine, you are giving up too much and not getting anywhere near the parts you need. Also the seller can't keep engine makes and models straight for pictures, and gives almost no information as to what the engine specs are. Even in the same year model not all 302 are created equal. Different heads, different cams, and even different firing orders for different applications.
It won't be brand new, but here is my suggestion for engine selection. I recommend the same regardless of EFI or Cargburetor, and manual or auto. Start with an Explorer 5.0L. It is the latest production engine with most of the best production components. It has the same firing order as the HO Mustang engines and it has the best production heads. The camshaft is not wuite as good as the Mustang unit, but it's good for a truck and easy to change while the engine is out if desired. Most importantly it has all the right components to support your swap. The Explorer 5.0L had thetightest front end accessory drive (FEAD, aka accessory package) of any production 5.0L engine., which means that it will have more clearance in a tight engine bay. First gen Ranger is the tightest of all Rangers so space is at a premium.
Any Explorer will likely have high mileage, but it is also likely in very good condition. Most Explorer 5.0Ls still on the road need little more than a hone, new rings and bearings, and a reseal to be nearly new. That's all that both my 180k mile Explorer engines would have needed if someone hadn't left one of the blocks out in the rain. That engine with a mild camshaft and a good set of headers would be nice in a first gen Ranger. I'd personally recommend the 96 or 97 Explorers for the standard GT-40 heads as they have better/easier header selection for your truck. You can likely get a complete donor for price of engine above, have better parts, and come out cheaper after you've sold or scrapped the left overs, especially if you have to buy the FEAD for the engine above.
If you want Carburetor, it's as easy as swapping the intake over, replacing the cam synchronizer with a distributor, and adapting the fuel system. For fuel I'd personally go with a slightly newer tank and run the low pressure intank pump with a regulator if needed. Someone with more experience there can help better than me.
I don;t know what 6 speeds can be adapted to the 5.0L, but none were installed from the factory. The T5 World Class manual transmission came from the factory behind the 5.0L, works well behind a basic 5.0L build, and seems to fit well in the Ranger.
Sorry if this is information overload, I get wordy when I get tired and should have been asleep hours ago.
Welcome Visitor! Please take a few seconds and 
