Don't worry too much about the package difference. The 1045 should be fine electrically, and its better package will only help longevity. You'll just have a small mechanical challenge to overcome.
CR1 and CR5 are "fast recovery" rectifiers. You *must* replace them with same. Current and voltage ratings are only the minimum things to look out for. You need a reverse recovery time of 150ns or less.
Replacements for C1 can be found at Digikey. However, the design is flawed, and that capacitor is simply the wrong type. I recommend taking four 1uF 50V ceramic caps and wiring them in parallel. Use that combination in place of C1. The combination should outlast the rest of the mac.
Ok, that said, I would not recommend just replacing components randomly to solve a specific problem. What is not working? What are the symptoms? Remember that the three most common problems are:
1) Bad C1 (causes either a vertical line or no raster at all). Usually easy to spot, as it will fail by shorting, then overheating. In response, the pressure will rise, and you'll get a bulge on the top as the pressure-relief slots do their work. The top of the cap should be ruler-flat. If it bulges, it's dead. Period.
2) Bad solder joints on yoke connector at the analog board. Just freshen up the joints with new solder.
3) Bad solder joints on flyback. Freshen those up, too.
A fourth, less common, problem is easily solved:
4) Misadjusted or dirty pots. Note their initial positions, then rotate them back and forth a few times with the unit powered off. Return to initial positions, try again.
For more details, see http://68kmla.org/files/classicmac2.pdf
Good luck!