Problem with replacement engine

I have a 1989 Mazda B2200 truck. Several months ago I removed the engine. A month or so went buy before I got a better engine put back in,then a few more months went by before I got around to connecting every thing. Now I am having some problems with getting the electrical correctly hooked up.I have searched and printed out every wireing diagram i could locate but none of them really give me a clear concise picture of what I need.
When I use a key (or a remote starter) to crank the engine it barely responds with maybe one or two slow rotations.
The battery is new,I have even tried with another battery to make sure. The starter is good and I am now at a loss at how to proceed.
What are the possible things I need to check ? A fuse? A inline fuse? wired wrong or incomplete?
What? Help please.
I know some will say to just junk it but the truck has sentimental value and would like to keep using it as a farm truck.
Thank you for any advice.

No need to junk a truck that is cranking slowly! Check your starter positive cable and connections, as well as check your ground connections. If they all look good you need to do a volt drop test on both the starter positive cable and starter ground. My guess is you have either a bad connection somewhere or a bad cable somewhere. Either that or the engine is damaged, turn the crank with a ratchet and make sure it is not seized up.

I cleaned both battery posts,the ground for negative side of battery and the connections and posts on the starter.I can hit the button and motor cranks a slow turn or two and stops.
what instrument (and where can I get it?) do I need to use to testcables?

I'll bet you its your ignition switch, there a problem on these trucks with all kind of weird side effects.

I would normally agree, I had to replace my ignition switch on my truck as well because it was causing some weird issues, but in this case, because of the fact that the starter is in fact cranking, but slowly, the ignition switch doesn't sound like the cause. If there was an issue with the switch the starter would likely just click and not crank at all, or do nothing at all.

To do the volt drop tests all you need is a basic digital multimeter, you can get a basic one for relatively cheap at radioshack or similar. This site gives you good instructions on how to test the system. In step 3, the red lead is simply touching the case of the starter.
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This is all assuming you have a good battery that is fully charged (12.6v)

Maybe,but if I am using a remote starter button connected on the post on the starter shouldnt the starter still spin and crank the engine?

Do you have the large ground cable connected to the passenger side motor mount area, and is it tight?
Sometimes when doing an engine change you can forget to tighten things up all the way.
Also, there is a short black #10 gauge ground wire that goes from the back of the head to the firewall......is that in place and tightened?

Red arrow shows the wire.



This is connected to the rear of the head.....when the head is on the engine that is!

As mentioned earlier by CyFi6 have the engine in neutral, get a ratchet and socket for the crank shaft pulley and see if the engine turns over easily. If it's still hard to turn over check the other engine parts with a pulley, loosen them, then try again. If the problem persists maybe a seized engine or a stuck transmission?

Get the starter and the battery re-tested. How do you "KNOW" that the starter is good ???