when I did mine (05 alloytec adventra) cam chain stretch wasn't my problem. I took close pics of everything before I took the chains off but my girl dropped the laptop on the floor & I lost the lot. I sent the heads away & the cam positions moved also. I used that thread above & google as I couldn't get help locally. read the whole thing carefully as there are some major corrections in the thread. basically I used the crank keyway position shown in the pics as the starting point & then lined everything up(cam & chain marks) from there. I had to use spanners to hold the cams in the correct position(keeping the valve springs compressed) to get the chains aligned with the actuators(sprockets). once I had all the chains & tensioners on I cycled the engine by hand to ensure no issues. it runs well now. I did chains while I was in there(although when I measured them there wan't any noticeable stretch).the thermostat was a cow, i'd suggest doing it while the intake's off(if you haven't already) & strongly recommend using hi temp sealant on the housing to pipe union. I cleaned & reset the chain tensioners at my workbench & used stainless paperclips(they're the perfect size) to hold the spring tension back till the time comes to release them.. good luck mate