1300 block (86 Venture-up) vs. 1200 block difference?

[DreamV4]

Stroke is identical 66 mm, 1300 was just bored 3 mm over from 76 to 79mm. I guess blocks are identical from same mold.
If blocks are identical, Vmax heads can be installed. Gears have different ratios.

 

[one2dmax]

That is close to correct. The 86-93 blocks are ideal swaps for use with Vmax's. Use the Vmax heads/cams which nets the same Vmax compression. Gearing is close enough to not be an issue (though the trans has the earlier design that was recalled for failures under Vmax usage). Expect approx 10% power gain.