Congratulations on the GX140 engine - I think a GX120 would have been more than adequate to do the job, but they are both nice engines. I don't recall the output shaft sizes - you may have had to get the 140 to get a 3/4" output shaft so you wouldn't need to replace the engine-side half of the clutch (the Kirby has a 3/4" shaft and I think the GX120 is 5/8" unless you get a variant version on special order). As expected for such an early machine, you have a one piece engine deck, which is perhaps just as well since the mower now has double the power Scott Bonnar thought it should have. (The later twin rail version seems prone to cracking the front rail at the inboard engine mounting bolt.)
I'll leave Deejay to talk about interesting features like the strips you've riveted onto the roller, presumably to help get up your hills, and how thick is thick enough for a bedknife. The reel looks to me as if it still has well over half its total life in front of it, but that is Deejay's territory.
