You may find there are issues with rechambering the affordable smaller caliber guns, in that they generally aren't built for the pressures or tolerances required by any of the unlisted calibers in modern production. Also, rimfire guns aren't ideal for conversion due to short cylinders, large gaps in the frame, loose tolerances etc. Not saying it isn't possible, just might not be worth your while. Best bet is a shot-out 44 or 45 cal gun whose chambers and bore are pitted and work from there. Mooncoon has made good suggestions in the past of using 297/230" Morris Short and .297/230" Morris Long cartridges - they're low pressure and can be made from shortened and thinned 30-30 brass if I remember right. If you're going through all the effort, better to refurbish a center-fire antique that's already in the cal you want. It'll be less effort and you'll spend less money and less time doing it, and you'll still get a ton of experience.
What you'll likely find is that most of the 32's and 38 rimfires are easiest shot as rimfires... adapter cartridges using blank inserts are easy and reliable and don't require massive overhauls on low value guns (where your increase in value in the conversion won't pay off the time and work involved).
