i have a good used BBC merlin 10.200 pro-block that is the best iron block made for big HP can go to 4.630 and have alot of iron left to take big hp block is a steel cap oring and bush lifter bores can be seen on e-bay item#230098255190 this block was never hurt and will hold water no block filler has alot of prep work all work pro done NO money was spared on this block thanks