'78 Blazer wheels onto 98 Tacoma

Wrong! They may match the lug pattern, but the Chevy wheels will have a different offset and/or backspacing (than the OEM Toyota wheels). This will result in more stress and wear to the bearings, etc. The tires and wheels will "stick out" more, raising issues in ethics (excess spray on adjacent motorists) and aesthetics (ugliness, IMO).

You can check and compare the backspacing on your existing wheels ans the new/used ones:

The bigger issue is actually whether the center bore of the wheels is large enough to fit over the front hubs on the Toyota. That is a common fitment problem with Chevy rims on Toyotas. MEasure the OD of your front hubs and check it to the ID of the used wheels to see if it'll be a problem.