attaching muffler-round to a square hole?

hi, I am new here and this is my first post. I have a Huffy cruiser with a 66 in it. today was the first day I was able to actually ride it. 1st lesson learned...take everything apart and reinstall using threadlock! lol. she ran like a banchie after I got the gas/oil mix right. Too good!

upon comming home it got stuck in WOT because the throttle cable came loose at the bars, my plastic spark plug wire socket shattered. air filter vibrated off its rubber, and effing with all that noticed I lost my muffler somewhere between here and there. lmao!

question is...I'm looking online for a new muffler, all mufflers found have a round flange but the exhaust port is rectangular. can the round flanged mufflers be attached to the rectangular port? and if so, do I use a round or rectangle gasket?

I am a aircraft mechanic by trade but currently a bodyman and painter at a local shop. traded painting someones Hood for this bike. before spring I plan on dissassembling it and painting the engine gloss VHT black, the peanut tank, fenders, and chain guard in waterbornepaint bright budlight blue with big metallic flake with silver ghost flames on the tank and some pinstriping on the fenders. and the frame a metallic silver. looking foward to it but want it to run more than a day at a time without problems. lol.

gained a lot of info on this site already and love it. I will be a regular. and will update pics on the paint. thanks

no, I lost the whole damn thing nuts worked there way of on the head. someone else built it obviously without any locktite. suprised I didn't notice running it over or sound change. the head has a rectangular exhausted hole, don't know about the lost muffler but there are both round and square exhaust gaskets on the market but can only find round hole mufflers for sale. gettin a bit confused

I have no idea either. I thought I would have heard something different but guess I was too busy trying to catch bugs in my teeth. lol. traced back on my pedal bike being that my spark plug wire cap blew up and then traced it back 3 more times in the car. there goes $25. oh well. thanks for the info