Generally...when a business includes "racing" in a title, the work won't be cheap.
IMO, stick with Butler...you get what you pay for. I would never have any rare block or a one of block machined, assembled and tested by anyone other than a Pontiac specific machinist.
If I had a general purpose engine built would I consider someone else. $3500 is ok for a stock rebuild, balancing, forged pistons, aftermarket rods, heads done and assmbled.
Si Vis Pacem Parabellum
1967 Starlight black PMD Engineering 400 Auto 1968 Alpine Blue 400 4 speed 1968 Verdoro Green 400 HO 4 speed 2013 1LE 2SS/RS Inferno Orange Camaro.
