Seeing the headlight switch on the pedestal, and the hydro transmission and lift, my guess would be a 149, since factory they had all 3. Plus, it looks like the blower housing is almost filling the frame (the 14's have a larger blower housing (flywheel/fan) than the 10 and 12's). But as said above, a 1x9 could have the lift and lights added. But gut reaction to me would be a 149 (my favorite model (Sorry Kraig))......
For the engine interchangeability.... best answer is sorta. From the 70-169, yes they will interchange. They all used the same oil pan, and when bolted to the frame, should all be in the spot for the driveshaft and the belt routing. However, you might have to swap some of the "bolt on" items. For example, the 70 used a pepper shaker muffler out the carb side of the tractor, bit the 149 uses an elbow and muffler that blows out the starter side. Earlier engines have dipsitcks that insert from under the hood, just beside the starter/generator. In the later 1x6/7' and in the 1x8/9's they had a dipstick on the cam cover, just below and in front of the carb. 70-1x6/7 have the gas tank mount bolted to the top of the engine and the battery is under the hood On the 1x8/9 the gas tank is on the pedstal, and the battery is under the seat. There are some differences in the "tins" on the engine, and sparrk plug location in the head. Now, if you are looking at an enging from an Quietline 800-1650, then there are more differences when it comes to the engine. They could be used, it is just much less bolt in, than an earlier engine.