Here is a 1974 455 olds we got for 100 bucks. Now we want to put this in my 78 trans am, originally a 400. Now I do not know a thing about motors, so from the pictures I can tell I need all the pulleys, water pump, new freeze plugs, new gasket set, new distributor and cap and everything. I want to do a new cam and lifters. And where can I get all this, from napa maybe? How many horses can you guys estimate this has? What do I need to do motor mount wise to get this in? Sorry about all the questions but I am just not a motor guy, I like body work. 
That's so beautiful! <sniff sniff>
Ok, for the pulleys you might find some right here off a 403. Same goes for the motor mounts you need (engine side - frame side are the same as the 400). Things like the water pump, freeze plugs, bearings, rings, gasket set, oil pump and so on you can get from your local parts house like NAPA. Hold off on the bearings and rings until you have a good machine shop check the crank and cylinders to make sure you get the size you need in case any cylinder boring/over-honing and crank grinding is needed. The machine shop may even be able to get you those parts themselves and install ones like the freeze plugs and cam bearings (wich are installed with a special tool). For the distributor, you might find a good used HEI (which it looks like it has). Again, one from a 403 will work.
Other parts like the cam set (You'll need new lifters and probably springs with a new cam and if you go much beyond stock you should/may need to change over to adjustable rockers and new push rods) you can get from
www.SummitRacing.com . They have good prices and last I knew charged a $10 handling fee, but no shipping. Headers are tough on an Olds 455 in our cars due to space restrictions, but ones from a mid '70s Cutlass with the 455 will fit (with maybe some "tweaking"). I suggest you lose the 80lb intake manifold and get an aluminum one. It won't work as is with the shaker anyway, so a drop base air cleaner like Larry Navarro's WFO unit will be needed (or some creative brackets like Rich has).
Let's ee, how many horses would that engine have stock? Probably not as much as you might think. They were starting to go with the more "air friendly" emmisions heads and lower compression pistons by '74. But they never had less than 275. But their best feature was their "frame-twisting" torque. I suggest some good frame connectors.
Let me know what other questions you have!
God I love those engines.
