No, they will not. Howa uses 4 mounting screws on top where the X-bolt uses 8. The proper mount for the Howa 1500 long action would be the models ending in x734. The 30mm - medium (extended) for example, 74x734. Unfortunately, we do not make a 20moa alloy lightweight for the Howa 1500. If a 20moa mount is needed, please check out our picatinny selection. The correct Picatinny Rail for a Howa 1500 LA, 20moa, is the PLM252150.
Thanks!