Does this sound like it'll do the job

It does look promising. I'm having issues getting details about their trans from them. I hate not knowing whats in the box because usually is breaks or falls out. I don't see why it's such a big secret? Some will only quote verbal without any writen quotes.
Supply and rebuild C10 to suit 700hp.
Transmission will include:
PTC Hy Tuff Input Shaft
PTC Chrome Moly 4 Pinion Forward Planetary set
Forward Pattern Valve Body (custom done via the builder not bought)
6 Friction Forward Clutch
6 Friction High/Reverse Clutch Pack
Kevlar Intermediate Brake and
Kevlar Low/Reverse Band
Added Needle Roller Bearings
New Lock Down Dipstick and Tube
High Speed Bleed Modifications
Modified Lubrication Circuits
Precision Machining
PRICE includes GST
C10 700 hp Full Manual Transmission $2200.00
Includes $ 200.00 GST
If your car has the ground clearance, a deep cast alloy sump will greatly strengthen the transmission assembly; provide more fluid and aid in fluid cooling. Add $220.00