Oldsmobileboy, i'll have to disagree with you. .50 or .60 gap is just too wide for a 260. Leads to a tendancy towards preignition at high timing. 307 heads on a 260 have too large of a combustion chamber without machining. As such, you will lose compression. On a motor with 7.5-8.5 compression stock, this is suicidal for power. the 307 heads will not match up to the factory intake. You will have to get the proper intake for the heads, or an Edelbrock intake for the pre-85 307 heads. Bosch platnium X1 plugs work well in the 260 Oldsmobile. The multi-contact plugs dont seem to work well. And Always check your coil and contact plates under the distributor.