its basicly no broplem.
heres a pic, where you can find bore sizes marked on the block.

but i strongly recommend that you measure what that bore size really is now, because the block isnt new. you should use dial gauge type tool foor that. whit it you can check if it is cone or oval shaped over tolerances. if you dont have that kind of tool, you might want to ask your local engine workshops (who builds or rebuilds engines).

here are some more spesific info about those standard bore sizes.

standard size bores:
1= 90.800 to 90.810mm (not used in Cosworth engines)
2= 90.810 to 90.820mm (same as in Cosworth engines)
3= 90.820 to 90.830mm (same as in Cosworth engines)
4= 90.830 to 90.240mm (not used in Cosworth engines)

standard piston size:
1= 90.765 to 90.775mm (not used in Cosworth engines)
2= 90.775 to 90.785mm (Cosworth 90.758 to 90.772)
3= 90.785 to 90.795mm (Cosworth 90.768 to 90.782)
4= 90.795 to 90.805mm (not used in Cosworth engines)

Cosworth bore to piston clearance:
0.038-0.062mm

All measures are in millimeters. im not sure what units you use, but its easy to convert them whit this wery useful program. and its free.

hope this is usefull for you.