need some advanced help
fill in all of the holes like these:

to look like this:

sorry if it looks like crap, but it was a quickie from paint. hopefully you'll get the gist. what im wanting to know is, what type material can be used to fill in these voids, and be durable enough to withstand the heat, engine shaking, and sanding (during paint)? after the voids are filled, im wanting to sand the "said filler" to make the intake look nice and smooth, without all of the reinforcement bars showing.
any and all advice will be greatly appreciated and considered.






