Louisiana Gov. David Treen's efforts to woo black voters are being closely watched by the national Republican Party, which hopes to use the results to forecast GOP fortunes with blacks elsewhere. Mr. Treen's Democratic opponent, former Gov. Edwin Edwards, had strong support from black voters in his 1971-72 and 1975-76 campaigns. On Oct. 22, he is expected to get a large majority of black votes. The Louisiana gubernatorial election is 1 of only 3 before the '84 presidential race - and the only one in which a Republican governor is running.