Bought a vacant lot in 1972, sold it last year. I have long term carryover loss, but my ? Is at what tax rate should I use to calculate the basis for the lot. My tax bracket is 15%, but I understand that, for any assets held for a long period it should be bracketed at 8% or thereabout. Maybe I am not making myself clear.

The sales of your vacant lot is the sale of a capital asset, so capital gains rates apply.

If your marginal tax rate is 15%, then YOUR capital gains rate is 5%.