No! Stop screwing them in if they don't go in easily! Pull the pulley off and then screw the bolts in so you can see if there's any interference issue. You can't see the issue with the pulley in place.

 

Jeepin, It seems from your note that the fan may still be loose? Is that right? If it is then as 71BB says, don't tighten any more. It's hard to imaging you cross-threaded all four, so I would be looking for that obstruction 71BB speaks of. If there is nothing in the way, did you put your fan belts back on before tightening the fan assy.? Possibly leave out the spacer between fan and pulley( I don't even think that is possible to leave out, just being thorough). Use the wrong bolts on the fan assy?
Might be a case of different, or beat up threads on the 'new' water pump. I'm assuming it's a rebuilt one. Run a tap through the threads on the water pump to clean them up an eliminate that as an issue. Let us know how you make out.

 

Do later pumps have metric threads?

 

Not sure Damon, but good thought. I believe all SBC water pumps are 5/16 NF thread.

 

I just had a thought....that doesn't happen all too often so I better write it quick. If this is the first time you've had the fan/pulley/water pump off in many years, you might have pushed some corrosion from the aluminum spacer into the theads of the water pump. That would make the bolts hard to tighten.

Let us know.

 

Alright guys so I got it done!!! After I asked the question about tightening my dad got home and just told me to keep on going!! So I did and it all seems to be good. I did have to put everything back together like the alternator and belt before I tighten to make it easier tho. But thanks guys ur help is really appreciated!!