ok so i have a 66 ranchero and it will start acting sluggish when i try to give it more juice , not a lot more just some, then after a little bit of that it will die and wont start back up like the battery is dead but the lights still come on and everything. then when i jump it it starts and then lasts for a bit but not long and i have to do it all over again. ive replaced the battery, alternator, solenoid switch, voltage regulator, and the starter has been checked. any sugestions?

 

Have you checked the battery cables to make sure they are clean and tight at the battery, ground and starter and checked the condition of the cables for cracks, broken insulation where dirt or corosion may have got in them restricting the flow of electricty. If the cables look good check them for burnt spots or weak spots that may indicate broken wires inside the cable.