Start with the basics. New plugs, plug wires, air filter, & fuel filter. Also check all vacuum hoses for leaks and cracks. If the truck is over 10 years old, or idles rough, just replace all under hood vacuum hoses. Very cheap repair. Do them one at a time as to not get confused.
Yes
It depends on what year your S10 is, need more info.
We need to know what year that S10 Blazer is.
An S10 is the same as a Chevy S10.
V4?
the starter relay.
fuel pump relay
The Chevy s10 was introduced in 1982.
Yes
Will a Chevy blazer engine fit in a Chevy s10 pickup
there is no thermosat on a 1944 Chevy s10. For that matter there is no 1944 Chevy S10
Yes they are the same