Need Help from You Stoker Gurus!!!!!!

You may not want to hear this, but buy a stroker kit. It will be more reliable than a ground down 400 crank.

I can tell you that if you use a longer rod, you need a shorter piston. Not for compression. The fact that the piston will collide with the head is your main issue. It gets to the point where you cannot compensate for rod length with shorter piston height because there is no material left in the piston.

You can adjust compression by using a dome, flat or dished (reverse dome) piston.

If you are sold on the 400 crank and you are going to use it anyway, call CHP, DSS or SRP pistons and tell them exactly what you have. They may be able to get you what you need. You are going to need a big dish to keep the compression that low with a stroker.

I understand. A stroker kit for a tiny bit or work and a set of pistons is not bad. My advice to you is to keep it under 6k. You can port those heads and intake for just the cost of the grinding wheels.