That looks like a great candidate for a rebuild! You should be okay without a cradle unless you remove the entire transom or cut the stringers out. Like Rick said you'll probably enjoy the porta bracket more but you may be able to get away with a bigger jackplate. Look up Hanson boats. They have a similar transom and use a jackplate.
Nice!. The outside skin of the transom seems to be in good shape so I would just leave that intact and cut the wood out from the inside. No racking will happen because the skin is still holding it's shape. The stringers look to be in great shape, like new.As for using a jack plate - you won't get enough lift to allow tilting the engine out of the water without hitting the transom. Start a search for a used porta-bracket and get it rebuilt and powder coated, as a lot of guys have done here during their rebuild. The Porta has a lot more articulation to allow tilting the engine out of the water without hitting the transom.
Great find! Looks to be a great start to a rebuild. I agree with what's already been said. Because the exterior transom skin is in tact and it looks like you left some of the stringer tops i would say working off the trailer would be just fine. However, i would run some 1x2 or whatever you might have laying around about every 4ft or so to keep from the hull side shape and from loosing its "memory". Without the floor it might want to start bowing out in the center section. You definitely want to do this if and when you remove the cap to re-core etc. and would go closer together at that time. Looking forward to following along with your build. What is your intended use when finished?
Fantastic boat! I am pretty sure I drive by this project every school day with my son on the way to King.. We are in process of fixing/rebuilding our 1971 Flatback 222.. Mine is currently at Cortez Cove to take a look at the damage. If I ever see you out.. I'll honk twice!