Streetmaster 318???
Here is a 318 combo that I am building right now on a budget. I have it together and just need to drop it in the dart. I may have $1200 into it. You can build a decent daily driver for pretty cheap if you are willing to turn a wrench. My advice would be to look for a set of Magnum heads from a Dodge/Jeep 318-360. They will bolt right up to your LA block and have closed chambers, bigger valves flow so much better. I pulled my set myself for $75 for the local wrecking yard. If you go with a moderate cam like me you can run chevrolet springs and retainers on them for much less than the mopar performace replacments. You will need the conversion pushrods through mopar performace. Here are the links on a couple of my posts.
http://www.forabodiesonly.com/mopar/showthread.php?t=65469
http://www.forabodiesonly.com/mopar/showthread.php?t=66298