aks801 If you are building the car to sell, a correct year 428 block is going to cost you big bucks. A 390 block can still be found for $500-700 with thick walls and plenty of boring room. A 428 block, a safe .030" is max bore for this motor. A sonic test would also need to be done. You are playing with a 40+ year old block to start in a 428. The walls where not that thick, same with a 427 block. Can you bore them out to .045"-.060" MAYBE depending on the sonic check and how thick the thrust wall still is. Very few people can tell a 390 from a 428 block without measuring the bore and stroke. I was caught in the problem myself. I got a motor and found out it was a 410 FE motor. A 3.98 crank with a 4.05 bore. Good thing is there is plenty of meat to bore it down the road if a want to use it. Some guys are cheating thin wall blocks with filling them partial up with block crete. Stablizes the block but make the motor run hotter from less coolant around the cylinder walls. Most heat is in the top 1-2" of the block and heads. You can drive these on the street but would not want to be caught in any traffic problems, these motor overheat even with the best cooling systems.
. Finding a 428 block and having it sleeved is another idea. For street useage I see no problem, hard abuse that's a different story. The 390 block with all the work is going to come in cheaper that finding a 428 block and having the machine work done too. Try and find a heavy webbed block if you are going with 428. Rick L.