yes,you can overbore the block to 76 mm easily,but it'll only give you about 1270 cc's.you used to be able to get factory pistons at 76.85 mm which gave 1298 cc's.this was good for an under 1300 cc race car.the a14 not only has a bigger bore,but a longer stroke to get the 1390 cc's.you also have to bore out the litle ends of the conrods to accept the bigger gudgeon pins.i feel it's a good way to get more performance out of the motor,if you can't just get an a14 or a15.