RYAN - Actually, the baffle is 2-1/2" tall, deck is 40-1/2" wide over-all. I have some tight spots around trees & stuff where this deck barely fits or I have to weed-eat.
The lip on the inside of the deck creates a channel for clippings to exit the deck from. My deck actually didn't have runners or the end piece on the left side when I bought the tractor/deck back in Jan. '81. That's the problem with owning things so long, too many chances to "Improve" them along the way. With the runners I've had on other decks like my 44A & 50C when turning on uneven ground the runners gouge the ground. Those spherical wheels on the front will not. The "roller" on the frt of the deck was really worn, hole in the center wallowed out. I just cut some sections of 2X4 with a hole saw as large as I could fit on the 1/2" bolt and still clear the nose of the deck, sanded them up a bit and they've worn nicely for over 20 yrs. I put a similar but wider roller under my 50C deck spring of '09 like Steve B did. But I used some scrap Oak for them. Roller on it is about 10 inches wide, located right behind the center blade. It REALLY helps keep it from scalping. I have replaced the spherical wheels one time since I installed them. They wore a flat spot across them about 2 in. wide. The wheels on there now are the newer "Heavy-Duty" ones with greasable bronze bushings. The old wheels became castering gauge wheels on my home-made dethatcher for the 3-pt on the 982
Those blades are for use with my lawn vac, not normal mowing. I have a couple sets of "Standard" blades for mowing. And yes, with the mod's and those blades it REALLY throws grass and pulls REALLY hard. Even with standard blades it throws grass at least 5-6 feet clear of the edge of the deck but seems to pull relatively easy until the grass gets 6-8" tall. It doesn't seem to waste HP trying to get the clippings out of the deck. As long as the grass is dry it will not windrow like most IH decks do in taller grass. If the grass is 10-12 inches tall then "maybe", but only sometimes, not a steady windrow.
I pulled the vac for several years with the K241 and if the grass was more than 4 inches tall I had to take half a swath even in 1st gear. With the K321 I have to be careful or I plug the tube from the deck to the blower/vac from too much volume of clippings. What's really NEAT to watch in the fall when vacuuming leaves is sometimes a full-sized leaf will roll & blow around in front of the deck for a second before it gets "SUCKED" into the deck. I have something like 60 Maple, Oak, Locust, Ash, and Birch trees that are getting REALLY big. Leaf removal in the fall is a really B-I-G deal.
I made a comment Friday that I didn't have to add steel to the left side away from the discharge chute, but I did. If you look closely at pic #4 you can see the weld at the back of the deck and the piece of added steel ends right about where the lip starts. I have a spare "bracket" that I made to hold the frt lip on and I looked for half an hour for it to take a pic and gave up.
The 44" & 50" decks already have a lot of these improvements except for the frt lip. They have a bigger discharge chute, the MTD kit for the guage wheels, etc. I think they would benefit from the lip also, but I'd add more mounting brackets to reinforce the front face. Maybe some day I'll mod-up a 44" deck for the 72. It's got the HP to pull one easily, just need to find the right combination of deck & mule drive to make it work.