Grumpy, I don't find anything about picking a timing gear setup that will support the stress levels of a specific engine. Now I'm not asking about the different features concerning the timing.... multiple keyways or the very expensive fully adjustable set costing $150. What I'm needing is when do you need a billet steel crank gear or when do you need BOTH gears to be billet steel ??? When do I need the larger .25" rollers ??? Or Double Roller sets ??? Also when looking at the DOUBLE ROLLER sets, many times they say "Will not fit behind stock timing cover." Are we talking about the plastic covers or will these not fit behind a short SBC water pump ??? Some general guide lines would be very helpful !