I have stock gaskets and bolts on my own Z as well as all the builds we have ever done and we have never had a gasket issue ever. The stock gaskets and bolts will hold 1200 HP easy. The only reason you will have a issue with stock gaskets is detonation or overheating. The cyl pressures with detonation is insane and with hard detonation I do not think any gasket or bolt will hold and if it does much other damage will result. Octane and tuning are key!