Building a 302 or 5.0 for gas milage

I need you guys to tell me what you think of my plans for building a gas friendly 302 for my mothers van . We use it for towing the boats witch is about a hour each way to the river . For towing cars and right now its my daily driver untill I get the mav on the road. The van has 3.50:1 gears weighs 5,500 lbs and has an overdrive auto tranny .

My plans are to put in a RV cam, do some light port work to the heads to clean them up , a 480 cfm autolite or a 390 cfm holley on a stock 4 barrel intake or a eldelbrock performer and put some headers on it if I can find any cheap enough. I would also like to get rid of all the vac lines and wires that are hiding the engine since only half of it is being used right now and none of it will be when I put on the 4 barrel. The only problem is the van uses the same dist as a 5.0 thats all computer controlled even though it has a 2 barrel on it right now . I`d like to know how hard it would be to convert it all to a DSII ignition system ?

Also I`d like to use a 5.0 roller motor I got but I can`t find an rv cam for one any where . Do any of you know where I could get one for it ?

Thanks

To build for efficiency look away from a 4bbl carb, unless the primaries are very small. The CFM rating of the carb should be matched to the CFM of the engine, so you need airflow data on the heads, cam, and intake before you can choose a decent carb.

An RV cam is an excellant idea, CompCams makes the best cams for mileage/pulling applications for Ford products (every cam maker has their "specialty", this is theirs).

For good low to mid-range power, long runners and a 2 bbl carb are the best, but they will NOT make good HP numbers. You also want the Compression Ratio (CR) to be 9.5:1 minimum, and 10.0:1 is even better. You can use forged pistons to prevent knock, but it may not be worth the added cost as you can often tune the carb and spark around it.

After the engine is all installed an running, take it to a shop with a chassis dyno that can simulate driving conditions (for driveability problems), and ask them to set up the carb and spark for you - and that you want peak mileage and towing Tq.