One of the things you are going to miss with the TKO, John, is the smooth shifting the top loader had. The TKO is abysmal as shipped from Tremec. The problem is multifaceted.
Some of it is the synchros and there are replacement carbon fiber faced pieces that do a great deal to improve the gear synchronization. Sometimes these new synchros have worn out quickly because of a difference in the angle on the gear's synchro cone and the lining face on the synchro. For the most part this has been fixed but there might still be some old stock skulking around out there.
Some of it is shift fork friction face related and many transmission shops today have the bronze shift fork facings to help in this matter. Some of it is yet still related to the shift rails and Tremec's OEM shift rail timing problems. The stock rails can not be fixed, they have to be replaced.
The one stop shopping spot for all the fixes (and I have not talked about the front countershaft bearing yet) is Liberty's. They can do the whole shebang (including the front countershaft bearing) for you at one place and one stop.
When you are all done with the fixes the transmission will actually shift very nice — not like your old top loader but quite nice. The headaches however are not over, yet.
Hiding inside your new TKO 600 is a Tremec created fundamental design flaw that affects third gear. As luck (or rather lack of prior planning) would have it third gear on the main shaft is misaligned with third gear on the countershaft. If you want to believe the Tremec engineers the misalignment is
only 0.140"!! Here is a picture of what it looks like;
The pic also shows the damage the incomplete tooth engagement causes when you hook up your power to the ground in third.
While the problem is fixable it involves machining off the third gear synchro, shortening that portion of the gear, then a respline of the gear for a replaceable synchro like used on the input shaft and finally making a spacer to move third gear forward on the main shaft to properly engage the countershaft gear.
This is a royal PITA when everything goes right. When things go bump in the dark it'll blow you mind and your patience. This is something Tremec has known about for a decade (maybe more) and chosen to do absolutely nothing about!
If you haven't purchased parts yet I would strongly encourage you to look at a T-56 Magnum. It'll fix you up with a land speed record sixth gear (0.63) but a fairly nice 0.80 fifth gear like the TKO RR option. Big differences are;
◉ The shift quality approaches that of your top loader,
◉ The trans is rated at 700 ft/lbs TQ capacity,
◉ The gear spreads/spacing make the car a dream to drive,
◉ You don't have to use the 0.63, 6th OD if you don't want to,
◉ The car drives beautifully on the highway in 5th @ 0.80 OD.
Real nice solution, essentially the same price, no reliability or U/G expense BS to get the trans to do what it should do right out of the box.
All things considered, not a bad alternative ...
Ed