Hi cap70,
Why not rebuild the one you have? A rebore, balance and blue print plus a decent stroker kit and mild cam you could probably get out of it for the same money as a new engine block. At least you will know what you have and not risk buying something unreliable, or worse, poor performer. Keep your old flywheel, harmonic balancer and inlet manifold as well, if they don't need replacing due to wear.
Unless you are looking for really big engine performance gains, but I guess that's not really where you are going.
From my research, the high HP engines will set you back over $12,000.00 up to $20,000.00 and that becomes an exercise where you need to consider things like 4 bolt mains, new block, forged rods/pistons, big camshafts, etc. Not really good value for a weekend cruiser.
I rebuilt my old block (after chemical clean, sonic test & x-ray) had the whole rotating assembly balanced and blue printed, then fitted Edelbrock Performer heads with Air gap manifold and a good Crane camshaft. I did go a little heavy with shot peened rods and hypotech pistons, but that was because the old stuff was not worth re-using in a high compression engine. Just for insurance, ARP bolts throughout and a main stud girdle fitted. The lot cost me less than $8,000.00 and although I am just running it in, the torque improvement and responsive high rev performance is staggeringly better than before.
My mechanical knowledge is self taught and I love a challenge, so this engine was completely assembled at home.
Save your money with an engine rebuild and put it into better brakes, suspension, transmission, if any of these items are not up to scratch.
PT
