I don't know how anyone assembles an engine without a shop manual, at least until they "learn" the engine. The book posted above is very good. You can download a shop manual for free here: The year doesn't matter too much, as very little has changed, IE minor variances in the camshaft front oiling
72 Service Manual
[ame="http://www.abodyjoe.com/pictures/Misc.%20car%20info/1972%20Plymouth%20Chassis%20Serv%20Man.pdf"]http://www.abodyjoe.com/pictures/Misc.%20car%20info/1972%20Plymouth%20Chassis%20Serv%20Man.pdf[/ame]
69 Dodge Serv. Manual
[ame]http://www.abodyjoe.com/pictures/Misc.%20car%20info/69%20dodge%20service%20manual.pdf[/ame]
70 Dart Challenger manual
[ame]http://www.abodyjoe.com/pictures/Misc.%20car%20info/70%20Dart%20Challenger%20Serv%20Man1.pdf[/ame]
71 Dodge Body Manual
http://www.abodyjoe.com/pictures/Misc. car info/71DodgeBodyManua
There are an number of tricks that can gitcha if you aren't awake.
1--Several guys have had oil pressure problems. You must make sure that the little core plug is in place, which goes in the vertical oil passage going from the rear main up to the oil sender. If the block has been completely stripped and hot tanked, the others are
The screw in plugs in the rear of the block---there is one plug BEHIND the other the outer one behind the smaller inner plug.
And there's one in the oil filter mount. Make sure the two are installed in the front of the block behind the cam thrust plate. I dearly hope you have flushed/ blown out the oil passages to clean them.
CHECK the cam bearings to be sure the oil holes are rotationally aligned. You must have oil flow from the cam bearings up through the oil holes to the deck/ heads, and you must have the holes aligned down to the main bearings.
Be sure to check bearing clearance, if you have no other method, plastigauge is still available. Any parts store that calls itself a parts store should have one.
With some of the comments people have made claiming poor manufacturing tolerance, I would CERTAINLY degree your camshaft, and absolutely check your balancer for proper alignment of the timing mark to TDC. The rubber can allow slippage of the outer ring.
Use the proper cam break in lube, and prime the oil system, etc, so that you can fire the engine right up and break in the cam.
Under no conditions should you use a plastic cam sprocket.