I wont say that 3.73 or 4.X rears aren't nice with an OD transminssion because they do work really well, But at the same time look at some of the newer vehicles that are running 2.8x gearing with OD transmissions, these cars and trucks may have a smaller tire diamiter but if you look at some of the tables changing from a 26.5" tire to a 28" doesnt change all that much. The biggest effect when choosing gears is the cam and how it performs. Most of it isnt the 260 or 268 duration but more on the line of the LC of the cam will play the biggest part or the how things will best work especially if its a cruiser. An example is in my 67 C10, I have over 500HP, 4.10 gears, 30" tires, the cam I was running 236/240@.050 Adv 286/292 on a 110LC didnt like running at baseline cruise of 65-70mph, basically my RPMS wanted to be at around 2500+, yet I swapped the cam to a larger 239/242@050 adv 290/294 but on a 112LC and now I can cruise at 65 without the truck bucking or needing to be cleaned out from what appeared to be loading up. The LC of 112 was the key to just a tad better idle quality and lower rpm cruise speed. Generally anything 114 and higer is also going to take away most any of the hotrod sound, the 113LC is also often used for marine cams and real popular with NOS cams and usually will have more of a choppiness to them. Choosing the wider LC will give a wider powerband vs the shorter hotrod cam 110LC which is more defined as to where the powerband is.
Your next issue is the transmission, the 200R4 is an excellant trans, (the later the better), as the early ones had there issues just like the 700R4 transmissions. Running trips may be an issue to properly setting up the detent cable, the other part is lockup converter, being you wont be running an ECM to control them and the opertion of the lockup generaly you can get around this by some of these kits that are available, the kits basically allow themn to lockup in 3rd & 4th gear or 4th only, going from 3rd non lockup to 4th lockup is a major rpm drop. There are kits available for most 4barrel carbs for the detent but not for a tripower setup using singles, although GM did use single barrel carbs on a lot of the 6's and they where produced through some of the era of the 200 & 700R4 transmissions. One reason why n my sons 50 build we opted to use highway gearing and a built turbo 350 trans.
Typical pricing for a rebuilt 200/700R4 on Ebay is $1200 w/o mods.
Turbo 350 rebuilt with good shift kit & shipped $500 Plus most average used rearends out there have the gears usually around 3.08-3.55 which work good with these. The 3.55's not so much if you like cruising the highways.
Used 200R4 and 700R4 your on your own as they have been out a while and may or may not have been propery taken care of, taking them to the local trans shop for repairs usually around $1800
