motor looks real good with that air filter on it
don't cut the air cleaner stud, just put one of
these on it
food for thought...
your using front old style mounts on the motor and a new style trans mount.
original would have been the main, heavy duty mount on the bell housing with the front mounts to balance the motor.
new style has the main heavy duty mount mid way on the motor and the lighter mount on the trans.
as you have the motor mounted; you have no heavy main mount.
under heavy acceleration and torque your motor is going to move a lot side to side.
i bought my 58 set up that way from the previous owner, i was replacing exhaust donuts every week.
i had a friend of mine sit in the truck and put it in drive under heavy accel with the brake on and then do the same in reverse
the motor moved 4 inches side to side, you can probably push the motor side to side by hand right now.
buy your self some side motor mounts for a 68 truck (parts store guys need a year), some 4x1/4 plate and some 3/8 thick wall tubing.
bolt the motor mounts on, cut the tube to fit on the main bolt and triangulate the plate from the top and bottom frame rails to the tubing.
this set up will keep the motor in place, i did all the fab work in a finished truck
it will be very easy to do with the front clip off your truck, tack everything in and remove it to do all the welding
you could even leave the front mounts in for the look