I picked up a very nice ROYAL three speed at the dump. I needed a pedal to replace a threaded rod that the previous owner had used. The pedal set I bought yesterday cost me $21 (nothing cheap back here!)but when installing them,I found the hole to be stripped. I could pay someone to weld the pedal on but my question is,would it be better to get a whole new inexpensive crank assembly? Are they standard sizes? Difficult to install? The exisiting parts are soooo cool. Heavy chrome and well made,I sort of would like to keep them,even welded. Also,the gears do not seem to work anymore and yesterday the cable on the rear hub snapped. Not a worry at the moment but another question I have would be, could I just buy a new wheel and have a no speed,rather than a three speed?
The best fix for a stripped crankarm is to replace it and the only tricky thing about that for you is finding a crankarm that matches what's on your bike closely enough that it will fit. Here, I would go on a search of local bicycle shops hoping to find some old inventory. If that didn't work, I'd go to swap meets looking for entire old British 3-speeds I could rob parts off of. You might be able to buy one of those for $10 or $20 and just use the parts you need. That would be a good way to get the cable, too FYI.
Another way to find old parts like this is to search on www.ebay.com. You're looking for a "cottered crankarm" or you could try searching on "3-speed crankarm" or "three-speed crankarm." You'll find anything and everything on ebay if you look regularly and it shouldn't cost very much. You might even find the exact crankarm you need.
You could weld the pedal on, but if you do that be sure the person who welds it gets it straight, perfectly straight. And ask him to use a welding technique that is reversible so someday if you find the right crankarm or if your pedal gets ruined or wear out, you can fix it. Oh, he has to be careful not to overheat the pedal axle or he'll cook all the lube out of the bearings and maybe even weaken the pedal axle. Putting wet rags on the pedal might solve this problem. The welder should know all about this.
On the wheel it would probably be easier to hook up the cable and get the 3 speeds on your bike working again than to switch to a coaster-brake rear wheel, and cheaper, too. So, that's what I'd recommend. Your bike will look the same but you'll have the nice benefit of 3 speeds, which is really nice when it's windy or you have to go up hill.
I hope this helps!