I can see by your picture you have a 26" wide core so the car should have enough radiator. If it runs cool at speed when making horse power and heat but creeps up or runs hot at low speed and idle when it's not making horse power or heat I would rule out radiator issue. If it's good enough to handle it under load it should have no problems under no load. To be sure the radiator is not clogged simply remove the thermostat and wrap a towel around a garden hose inserted into the empty t-housing. After disconnecting the lower hose from the radiator run clean water through the block until all watr coming from the block is clear. Next, re-connect the lower hose to the radiator and remove the cap and flush (back flush actually) until clean water comes out of the filler neck. This doesn't mean it's not clogged somewhere in the core. It just means no loose debris remains to the best of your garden hose ability. A power flush a better way to go but could entail buying some equipment or going to a shop to have it done. Drop the thermostat to 160 to get the system opening earlier and a Mister Gasket 160-S is my go to stat. The "S" tell you it has little larger opening than the stock stat for that car but not so much as to push coolant through the radiator to fast to cool or drop temperature. I personally don't like fan clutches on my cars because they almost never spin the fan at max RPM's at idle when I need it most. For best air-flow at idle I use a small spacer to get a 1/3 in and 2/3rds out spacing on the fan which will produce the air-flow possible. (I use an air-flow meter to check this so you don't have to) I also prefer a 7 blded flex fan over any thing else. If the new water pump is stock give it a whirl but when I do a cooling system I replace all water pumps with Flow Kooler pumps of San Louis Obispo. They increase the flow by about 10-15% and no more. High flow pump will have a tendency to increase flow to a point where the coolant doesn't spend enough time in the radiator compared to the air flow the fan produces at idle and will cause the same overheating as restricting the flow would. BTW, your overflow bottle needs to be an open system to work properly. Your bottle looks like the 2" garden variety and may not hold enough capacity for that engine. A hot system will puke when shut off under pressure because it's absorbing more heat and expanding the coolant but during cool down the sealed engine and radiator system will contract and create a vacuum that pulls coolant back into the system to keep it full and eliminate any air in the system. If the bottle ever goes empty during this process it means it's not big enough for the engine and system size and needs to be replace with say a 3" or larger bottle. Pulling air into a sealed system from an empty bottle is bad news and keeps radiator shops busy. Make sure the overflow tube from radiator to bottle has no leaks and bottle can puke out on the ground when full and never goes empty and your good to go. My go to : Mr Gasket 160-S super stat, Flow Kooler water pump, and a 7 bladed flex fan (pulls about 6 MPH air through the core at idle when measured before the grille vs 1-3 MPH for most electric fans measured the same way) and a spacer that put your fan 1/3 in the shroud and 2/3rds out of the shroud for best measured air flow. BTW, a good way to check the radiator for clogging is to simply put your hand on the front of the radiator core after it's warmed up to see if you feel any cool or cold spots in the core. Easy access to the front of the core and not yet hot enough to hurt you so check for cold spots the almost always means no flow... Don A
