Since the principal ""Presidential contenders,"" unless submerged in a diving bell within some neutral sea, are unlikely to rally round for inter-sectarian debate, this gathering of incidentally illuminating interviews is as close as we'll come to simultaneous weighing and measuring. The television version of the interviews, (which will be foreshortened with the Lindsay interview excluded) will appear betimes, but the ""unexpurgated"" book and the fair-haired British impresario-entertainer, David Frost, are sure to be touted in all media. At first glance all men perform predictably, and there are no unusual revelations. (It is hard to believe that Senator Kennedy's numerical recall about Bay-of-Pigs hawks was released on a boyish impulse). However, the degree, to which wheels of intellect churned, or ground to a screeching halt--the degree of ease and sense of adventure with which the various gentlemen have cut through to their present stances, is remarkably evident on the printed page once you have removed the wreathed smiles and resonant public voices. Except for the interview with George Wallace in which David Frost succumbs to the joys of skewering, Mr. Frost's queries are stimulating-to-mildly-silly, but are skillfully placed and constructed to bring forth a variety of responses. For Presidential attitudes, McCarthy admires Truman most; Reagan thinks Americans are puppy dogs; and Lindsay--not surprisingly after that last record budget--admires Don Quixote. A lively, quick study before the main event.