[Licensed to kill]

I'm in the process of assembling my engine and find that neither my crank gear nor my cam gear have have timing marks (other than the dimple or TDC). To my hillbilly way of thinking then, when I put the cam gear so that the dimple aligns with the pin hole in the cover, that is TDC firing position for cylinder #1 and is directly across from the crank gear. So, if I put the #1 piston @ TDC and line that dimple up with the crank gear, that should be TDC firing position for #4 (because it is directly across from the pin location) and should be right. However, I've read where to set the cam timing with a crank gear that has no mark that you use the key and line up the mark on the cam gear with that (if you have one) but when #1 is at TDC, the key in the crank is no where near the cam gear. This little tidbit of info casts doubt on what I otherwise think is correct. Any clarification would be appreciated.