not sure if my W/C circuit config is OK?
 

is this setup a BAD idea: i have a pump(MCP-350 modded) and heatercore( '77 Bonneville) in an external box at ground level. the CPU and GPU blocks are two feet above. would it be unwise then, to have my resevoir connected after the waterblocks and before the rad. like this: pump>waterblocks>res.>rad. also, the res. is physically located between the blocks and rad., elevation wise.
thanks for any help.

Re: not sure if my W/C circuit config is OK?
 

If both barbs are submersed in the reservoir, then the relative altitude of the reservoir is inconsequential.
I strongly advise the reservoir to be located immediately prior to the pump, with the shortest run of the largest diameter tubing and barbs you can handle. You've modded the MCP for precisely the same reasons as this recommendation.

Putting the reservoir where you have it should be OK. It will now introduce restriction where-as prior to the pump it is largely neutral. The pump will now be sucking through the radiator which our pumps hate. Otherwise, if the radiator is restrictive enough, it will cause the reservoir to be a pressurised component and thus it needs to be leak proof to a couple of PSI.

Best avoided.