You use a converter that matches the transmission. Some powerglides use a TH350 or TH400 input shaft, and if that's the case, you tell the converter builder-and he'll build it as such. If you have powerglide splines, you get a powerglide converter.
Flexplates. There are several. The JW "the wheel" plate has been known to crack at the ring gear welds. I do not know if JW has addressed that issue as of lately. Meziere makes a good one, and the PRW flexplate is the cheapest of all of them, and they seem to work well. Never had any problems with them. Make sure you get the right flexplate for your engine's balance (zero, 28oz, 50oz), and as mentioned, the correct tooth count for your bellhousing. The JW bell's are marked at the top, such as SBF-PG164 or SBF-PG157. There really is no benefit of one over the other (164 tooth or 157 tooth), they are both the exact same bellhousing but the starter holds are drilled differently. Most of the aftermarket flexplates are drilled for Powerglide/TH350/Th400 and also for Ford 4 stud converters, but it's always good to ask the seller. I get a lot of PG stuff and associated hardware from FTI and TSR. Both are fast, reasonable, and best of all they are racers and understand our needs as opposed to the Jeg's/Scummit salesepeople that are just phone jockeys (for the most part). FTI has a lot of informative videos on Youtube if you have some time to kill. He put one vid on there about how the torque converter works and what component does what, pretty cool.
The 1.82 will work but don't get real hard on it. Transbrake is probably considered no bueno with the 1.82 planetary. The 1.82 planetary is not nearly as strong as the 1.76 is-BUT it's lighter and sometimes a hundreth faster in a heavier and/or lower powered car. The dirt track guys use them exclusively over the heavier 1.76, at least around here.
I've always just used a stock style Ford starter. Most of the time, we just use the el-cheapo DB Electrical high torque PMGR starter, and it's cranking all of them fine. Can't beat it for the money. One or two of them, the bellhousings have been machined weird and the starter wouldn't line up properly. Easy fix.
That and the only other issue I've had with the JW bellhousing-seen one or two that needed offset dowels in the block to get it indexed properly. Just like a stick shift.