Ill chime in here. Monster Work Saws is in Oley PA. Its a legit outfit NOT a scam as someone has suggested. Most here never heard of them since they are small and frankly most arborists are too cheap to spend the money on a worked saw. Their largest percentage of clients is the logging industry. They dont need to advertise much since they have a large and solid repeat customer base. They have been building modded Stihl and Husky saws since about 2014 backed up by Bortz's Saw Shop which has been around since the 1950's. Most of you reading this have parents who are probably younger than that saw shop...
My oldest is a 4 year old 261. To date they have built me 2 200s, 2 661, and my 261. They are all real runners and reliable as an anvil. All 5 of them are in my bucket truck and used daily.
Ive also ran a few of their modded 362 and 462 and the 462 is a beast. Not the torque of a 661 but if you run it like a dirt bike and keep it in the powerband it really slices.
I won't speculate too far on this but what I have seen saw shops run in to consistently when people want to rebuild old saws is lack of finances to do it right. These guys won't hang their name on saws guys don't want to do a full rebuild on because when the crank flies out of a high hour saw that some armchair internet saw modder wanted to port polish retime etc but the bottom end was shot...the first thing everyone will say is that shop built them junk and it only ran xx hrs and came apart. Fully never disclosing to cyberspace the saw had 500 hrs or so on it prior to the hotrod work.
In regards to the 084, I would guess you wouldn't want to pay them for the time it would take to track your parts down etc.Those older saws are tough to get parts for. Not impossible but as you found it wasn't in some amazon click to order site either. But if you get everything needed and give them a call they may build you a hell of a saw. Probably better and cheaper and longer lasting than all these shiny sticker work saws flying around the internet in my experience.
Ill close with if you dont truly know how to sharpen a chain keep your money and dont buy a hot rod saw. No amount of mods will offset poor chain sharpening skills