Ok...not sure who said what here but here is the deal.
GenV = $500 or less iof you know where to shop
GenV LIM = $50? Or so...like I said...shopping
New GenV S/C gasket = $10
GenV to L67 TB Adapter Plate = Whatever ZZP wants for one...
So...$700? And that's being generous...if you DIY stuff it can be had for less.
GenIII vs. GenV
The Generation 5 M90 is a WAY more efficient blower due to the intake side of the case and rotors, outlet, etc. It is technically still a "M90" but its way different. Dropping pulley sizes on a GenV is also tougher since it takes less parasitic loss from the motor...thus causing less heat...less KR...but it doesn't take a tiny ass pulley to make the power, like on a GenIII. A nice guide I like to use is this...
GenIII 3.8" = GenV 3.8"...stock for stock...its fine.
GenIII 3.4" = GenV 3.6"...this is where it starts to get a bit different
GenIII 3.0"-3.25" = GenV 3.4"...even smaller for the GenIII, starting to get close to machined snout time
GenIII 2.55"-2.8" = GenV 3.0"-3.25"...keep in mind...knock at these levels are WAY more dangerous than on a 3.4" setup...1-2* of knock on a 2.55" is like 8-10* on a 3.4"...just keep in mind.
BUT...the GenV is a great swap for those on a GenIII who are running out of pulley size...like the OP. Hence why I suggested it. ESPECIALLY if you don't knock on the 2.6" with that GenIII.