Welcome to the Team Den!
Is it Den or Dan? If it is Dan you can edit your user profile to fix it, if it was a typo.
As to the cheap center carrier bearing. I don't know if it will fit or not as I have never bought one. The only vehicle I have put a carrier bearing into was my 1961 3/4 ton pick-up truck that I converted over to a full one ton truck to tow my trailered race cars. The conversion required new front springs, spindles and hubs for offset wheels up front and a heavier set of springs and the rear end out of a dump truck in the back. I retired the 235 in favor of a SBC 400 with a five speed Muncie out of the same duce and a half dump truck. That is why I had to rebuild the drive shaft with the e-brake bolted to my rear axle pinion.
A word of caution on those cheap import bearings (they are generally made in India or Pakistan). They are cheap for a reason. The materials are cheap and assembled by illiterate farmers that follow a picture on the wall showing the procedure. Since they are rarely if ever paid they frequently quit after a few weeks to be replaced by a new farmer a day later. This is a serious problem because neither Moog, nor Eaton make these parts any more. You have to look at a Timken bearing encapsulated in bright yellow polyurethane as a replacement part that runs a bit over a hundred dollars. It is all American made for your car, but the bright yellow plastic is a dead give away it isn't a stock part.
The Saginaw four speed is a direct replacement for the fully synchronized Saginaw short three speed (6" tail shaft). You may have a Borg-Warner three speed in the car if it came with a 348 originally as that was the transmission Chevy used behind all big blocks as the default transmission (the Muncie four speed introduced in 1965 was an Optional no cost upgrade, not the standard transmission. Though in your car it once again would have been a Borg-Warner T-10 transmission. The T-10 didn't last long behind a 409 which is why Chevy built the Muncie transmission to replace it behind big blocks. The Saginaw 4 speed was used behind small blocks that were factory rated at 300 or below horsepower, so it will service your 283 just fine.
Repeating myself the Saginaw short tail shaft three speed that looks like a four speed missing reverse interchanges directly with a Muncie or a B-W T-10. If you have an itty bitty non-synchronized first gear manual box with a really, really long tail shaft you have an early Saginaw from 1955-'58 that was used behind a 235 six and it will not interchange with anything. Beginning in 1958 they synchronized the first gear, and offered an over drive option turning it into a four speed; but they are very rare (the OD tail shaft, not the synchronized first gear.)