motor fitment

i am fitting my motor - my kit mounts are gm - i am installing a sbf....so i have to make a different adapter.....any idea how high the top of the carb should be? does the engine sit level? looks like my valve covers are lower in the back than in the front when set on the existing mounting block....

When swapping engines, you normally level the carb mounting pad (0*) on the intake with the car at ride height.  It is correct that the the valve covers will be running downhill to the rear.

This will "usually" give you approx. a 3* angle on the driveline down at the rear. Be aware that not all intake manifolds have the 3* angle built in.  It depends on what vehicle it was intended for.  Sometimes the engineers changed the angle to install an engine in a specific car.

As for the height, the simple answer is that as long as the air cleaner and/or other accessories clear the hood, you're good.  In reality you need to look at oil pan to ground clearance, front accessory pulley clearance, fan to radiator relationship (if you're using a mechanical fan) and where the exhaust manifolds (or headers) will fall.

Since it sounds like you will be fabricating your own mounts, you have some leeway in what you do.  I would try to get the engine as low and as far back as you can.  This will lower the center of gravity and get the front/rear weight distribution close to 50/50.  Better for handling.