check Mendeola Powertrain, They have a synchronized transaxle with chevy bell around 10K. They are doing a sequential 5 speed for me with twin 9 inch clutch disks
Talk to Ian
I talked to Chris at Weddle they sent me to Ian, Weddles stuff is mainly offroad and the gear ratios weren't great for a road car.
Ian will make you what you need. My SLC will start out at around 550 to the wheels but Trans was built to handle up to 700