Welcome. I believe you have a Lawn King, Which is much, much newer than 1980, It would be a 2002-2007ish model. Last of the true Rovers before the clipper (made by Murray) came out. I remember them brand new in the show room.
As for the spring in the picture, after studying the manual, I reckon that spring goes forward and attaches to something up near the brake pedal? I cant make out half the part numbers. It would be a tension spring to tighten the belt going from the engine to the hydro, a belt that disengages when you push in the brake.
As for why those bit are coming apart, I am not very familiar with the underside of this model, only ever worked on one or 2, but have a look for something seized or in the wrong place.
As for the spring on the deck, There are only 3 down there, the 2 big long ones that pull the deck backwards, and there will be a smaller one going from the tensioner pulley bracket to a bolt over near the left rear wheel.
Genuine parts for these are certainly extinct, have been since MTD bought rover, so if you cant heat and bend a new loop on the end you would have to find a mower shop that might have something similar from another brand.
