"We have also recently discovered that the used IW damper that they sold to me as an 18% is actually a 10% (shop is swapping on a smaller blower pulley to make up the difference on their dime)."
I don't know anything about your build*, but if it were my build I would not accept a "smaller blower pulley".
I would get my Marauder out of that shop.
*Assuming the 18% is a fit.
1/4 Mile Time 11.542 @ 121.19 MPH
195,000 Miles & 275+ Runs Down the 1,320’
541.57 RWHP & 476.64 RWTQ on DynoJet
Tuned by Aric at Injected Engineering
Vortech Super Charger V-2 “T” Trim, 19 PSI
8 Rib Belt, Innovators West 10% Overdrive Dampner
Air to Air Intercooler, Mini-race Bypass
Ford Cobra Remanufactured Long Block
Snow Performance Water-Methanol Injection
Kooks Headers & X Pipe
GT MAF, 60lb injectors, Dash 8, Aero Rails, Twin Ford GT Pumps,
Kinsler Fuel Filter, Kenne Bell Boost-A-Pump
Monroe Sensatrac, Metco Control Arms, Addco Rear Sway Bar
31 Ford Spline Axles & Detroit Truetrac, 4:10 Ford Racing Gears
Dynotech MMC Driveshaft
A-1 Performance Trans, Forced Tailshaft Lube, Carbon Clutches
3,500 RPM Stall Precision Industries Torque Converter
B&M Deep Finned Trans Pan
AeroForce Scan Gauges , Auto Meter Oil, Fuel & Boost Gauges
Kenny Brown Dead Pedal, 35% Tint, Silver Star Head Lights
AutoPage Alarm RS-727LCD, Boston Acoustic NX87