Can I get a /6 in the 7's?

It can be done, but as previously stated, it will take work and money. I have my 66 Valiant and 66 Cuda running low 8's in the 1/8, and low 13's in the 1/4. I don't have a lot of money in my cars, but I have been collecting parts for many, many years. There are many sources for new parts, but used part sources have dried up, and new prices are much more now. If your trying to prove a point with the slant, go for it. If you just want to run 7's, much easier with a V-8.
Another source for slant six info is www.slantsix.org