Best is a term that mean one thing to one person and another thing to another person. My opinion would be the get you a nice 302 (5.0L) V8. Solid dependable engine that can be made to put out plenty of power with the right parts which are plentiful and cost effective. Of course you could go bigger with a 351 but the extra weight and cost would make it my second choice.
10w30
.024 to .026 point gap for the 200 cubic inch straight 6 cylinder in a 1967 Ford Mustang
On a 1967 Ford Mustang : * If you have the 200 cubic inch inline six cylinder engine : The spark plugs are gapped at ( .032 to .036 inch )
The cost of a 1967 Mustang is dependent upon how the 1967 Mustang has been restored. A fully restored 1967 Mustang can bring is much as 80 thousand dollars at auction.
Chevrolet Impala
The 1967 Ford Mustang had hydraulic brakes
On a 1967 Ford Mustang, the oil cap is located on the top of the engine, specifically on the valve cover. It is typically a round cap that can be removed for adding oil. The exact position may vary slightly depending on the engine type, but it is generally easy to spot at the front or rear of the engine.
According to one of Fords websites : For a 1967 Ford Mustang 289 cubic inch ( 4.7 liter ) V8 engine : ( The spark plugs are gapped at .035 inch )
6Jx14 ET12
.024 to .026 inch point gap
that all depends on what engine is in both vehicles.
With engine running, ensure system voltage is in the 13-14 volt range.