Just finished the front brakes on my 66 E-Type now tackling the rear. Is there anyway to pull the rear calipers Pistons without dropping the rear suspension?

Drop the cage Lee, you will not regret it.
And once you do you will understand why.
And change your discs and diff seals as well, very easy if your bearings are in good shape, you won’t have to mess with preload and such, just mark and refit as before. If they aren’t, an other good reason…