The 305 won't fit that bellhousing.
You should be able change bellhousings to get that motor in front of the existing transmission. Since the foot starter mounts on the bellhousing and operates the 6-volt thype starter, I don't know of a way to keep the existing foot starter with a V-8.
There is no reason you can't mount a switch on the floor that would operate the starter.
You can use the bellhousing from a '55 to '67 (about) V-8 powered truck, or '63 to whatever six powered truck to adapt the 305 to your existing transmission. However, the mounting pads on the transmission will not match the existing crossmember. You could swap to a '54 or '55 1st crossmember.
I believe there is some trick to making the clutch linkage work, but I don't remember what it is.
And of course you'll have the common exhaust manifold steering box issue...
