Motor plate thought?

My 1973 scamp will be getting the motor installed soon. I was going to install from below with everything attached. Now I am considering a motor plate. I guess I could install as is and then install the motor plate. I will be getting the AR Engineering one from Mancini. My questions are..
1. Is there any benefit to keeping the motor mounts installed as well or is that not necessary.
2. I know that I need a spacer for the crankshaft pulley. What other spacers needed as well? Alternator? I have the AR alternator mount kit for Denso Alternators.
3. Is this going to create more problems with clearance of the fan to radiator?

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