Can someone help me estimate my HP

IMO, the Big Mutha Thumpr is too big for a mild build 318. If you want a Thumpr cam, go with the regular Thumpr. Somebody has some 302 heads listed in the classified section that are cheap and work well on 318's. An Edelbrock Performer intake is a good intake for a street 318, or you can go with an Air Gap, but I would stick with the Performer for the low end street torque. Get some Dougs or TTi 1 5/8" headers, and you'll have a fun street car with the sound you want on a budget. You can even skip the headers for now if yor budget is tight. I ran a similar combo in my Duster before I built the stroker for it and could smoke the tires pretty good with a traklok Dana.