Installation instructions:
Place biff.wft and biff.wtd in vehicles.img
Copy the following handling/carcols/vehicles lines into handling.dat/vehicles.ide/carcols.dat


Handling.dat
BIFF        25000.0  80.0  200	0.0 0.3  0.0  		1.0  1  0.16  1.0 40.0	0.3  0.50 0.2  30.0		1.62 1.60 15.0 0.10 0.45		2.2  1.3  2.1  0.09 -0.10 0.0  0.44  		0.5 1.0 0.8 1.5 	0.0  25000 		8440010		22				2

Carcols.dat
biff,		89,0,0

Vehicles.ide
biff,		biff,		car,		BIFF,		BIFF,		VEH@TRUCK,	VEH@TRUCK_BA_XX,	10,	999,		0.3171,	0.3197,		4,	1,	1.5	,1,	big+avoidturns+ext_strong+truckfirefx+truckexhaustfx+truckenginefx

Make sure to backup your files, I'm not liable if anything breaks!