Best Budget Build Motor

Since you have the 5.2/318, check out the cylinder bores. These engines are known to still have cross hatch from the day they were machined. If you still have them, IMO, is skip the new slugs and just mill the heads a lite bit. Mic up the motor and figure out how far down the hole the pistons are and cc the head if you can. Get the cylinder head gasket specs and plug all the numbers into a calc for ratio. You really do not want to go past 9.5-1 for a street engine. 9.0-1 is just fine. Besides, you'll gain more from the head flow than you will with compression.

Where you want to focus is the heads breathing ability and then onto camshaft selection. This is were the engine will make power (with the heads) and recieve it's thumping orders from. (The cam, which dictates at what rpm it operates at and in.) later on down the line, you can pick up some EQ heads and have them set up ready to blot on with the head cc amount all ready worked into it and the valve job done, ported if need be.

While head work costs a lot, it can be the last thing on the list to do and you'll be rewarded with a good driver until you bolt on a nice power upgrade.

From this point, the compression ratio and cam should work together and be matched to a rear gear ratio and stall converter for the vehicle it will go in.
Everything else there after is simply basic bolt on's. Headers, exhaust, intake, carb, and what ever.

Even the stock heads, which may not flow so great, can perform very well. Getting 300/325 out of the stock long block should be easy to do. A mild cam can do this. Something like 210 or 216 intake duration @ .050 will do it. I myself would not really go beyond a duration @ .050 of 230 unless I was north of 9.0-1.

The use of a O.D. trans would be a real big help. You could drop the gear ratio to 4.10's and then get into the OD for a final drive ratio of 2.82.