I am wondering, OH where are my manners HELLO Roboleg welcome to the forums! OK back to work I wonder if there is a termanology issue here? the OP says he does not want to change shifters and derailleurs but is asking about a freehub. I suspect he is confusing they types (or likely some
Fred mechanic got him screwed up)
this is a stnadard or "freewheel' rear hub, meant for use with a threaded freewheel. most likely what Robo has now. (yes I know you C&V geeks know the difference this is for the OP)
and here we have a "freehub" meant for use with a cassette.
there is no reason Roboleg could't use a freehuband continue to run his friction system. he will just have a few more gears.
there are lots of nice Freewheel style hubs on Ebay and in the trade and forsale sections here. also Roboleg unless you are doing the work you may want to shop for prebuilt wheels. labor and spoke cost can really ruin a 'good deal' on a pair of rims.
OH YEAH what randy says is uber important. if you go with the wider freehub gt that frame respaced