Looking over manuals I draw a conclusion that this is a modified QS-16 ...
MODEL 1660 (QS-16).
The motor is a swap out (should be KOHLER ENGINE ASSEMBLY (K341AQS) ) and side stack is a modify, too.
Front grils replaced and headlights added.
Seat is not original.
But, if all is working why worry? Looks cool as it is.
Welcome to the forum.
The seat has been changed to a regular tractor seat, but the grille as the original. The front end has been modified for the rectangular headlights, but i thing this was only done because the poor parts market here in DK for these tractors.
Also the muffler has been modified. The original muffler would be under the hood and the "exit" would be out out in front (i think)