well, there's a number of ways.

1)look for high comp pistons. The std A14 piston has a substantial dish. I've used mitsubishi pistons with a higher compression height. I think they were 4G32 pistons - but don't quote me on that, the details are all a little sketchy now as it it was around 8 years ago! The std size mitsu piston was an odd size overbore for the A14 . The mitsu piston had a slight dish, which was milled flat, and still gained about 1mm of compression height from memory.

A good look through a parts book will give you specs on pistons. You're looking for the same pin size, with appropriate bore (remember you can get various oversizes) and appropriate compression height and crown profile.

2) or you can deck the block a little. calculate your CR as the motor is now, and see if your target CR is achievable by decking the block. Just don't go too crazy with this method - as a rule of thumb, I'd limit the cut to a max of .060". This is better than decking the head, as the head remains serviceable, and you get a greater increase in CR for the same amount of metal removal, because you are taking material off the full area of the bore, rather than just the area of the combustion chamber. With an ohv motor, there is no timing chain to worry about, so as long as there is sufficient adjustment in the rocker's grub screws, there isn't much to worry about - valvetrain geometry won't change significantly.

3) if you have an open chamber A14 head, you can have the chambers built up with weld, milled, and hand finished to wedge style chambers. But that won't be particularly cheap. Better off looking around for a closed chamber A14 head (but you might already have one - won't know until you remove it).