Chevrolet Repair: truck will not downshift when floored, chevy blazer, spring tension

Question
I recently had my truck in the shop to get a new engine installed in it.  They also installed a new detent cable. now the truck will not down shift when floored. It is a 77 full sized chevy blazer with a new 305, slightly pumped up V-8 in it.  they did such a bad job with my truck, I will never take it back to them, unless the engine blows up or something.

Answer
It has a cable connected to the throttle, on the right side of the tranny.
They may not have connected it properly, or adjusted it correctly.
Find that cable at the throttle body, and see if there is any spring tension on the cable from the tranny when the engine is off. It should.
If it doesn't have any till you pull the cable quite a long way, kinda slide your finger off when the tension is fealt, and let it pop back. That will sometimes free up a stuck valve in the tranny.
You can open the cable housing near the starter, and see if it is connected.

Van