You have a great setup-- twin small blocks in a 26' cat. You have all the hardware and now need it pieced together. I would pull the motors and take them to www.Lingerfelter.com and let him rebuild and tune them. Let him do as he wants with all your parts and then just turn the boost down for about 500HP. You'll have room to grow and the motors and drives will survive.
350CID= 1.1hp/cid=380HP + 5 lbs boost (+30%) = 500HP!