WNting to put 17 inch wheels on my 64 dynamic 88 but I need the offset

 

Welcome. Just about every RWD car GM built in the 1960s and 70s (including your 64) used wheels with zero or near zero offset. There was enough room in the wheel wells that the stock tires had no clearance issues. If you don't go crazy on width, zero offset will usually be fine. If you are pushing the limits to fit the fattest tire possible, you can usually pick up a fraction of an inch or so of additional clearance with careful selection of the right offset, however this almost always requires a custom rim, so I don't think that's what you're planning to do.

And obviously don't confuse offset with backspacing, as most wheel vendors list the backspacing number.