Wanted 8372A Agnus chip and 5×44256 RAM chips

[Motormouth]

Yeah you are right about the 8372a.  Whether you do the motherboard ram upgrade or the trapdoor upgrade, you will need the  8372a for one meg chip ram.  Most 6a (but not all) motherboards came with a 8372a already on them.  Commodore had already ran out of 8370 and 8371 s at that point.

[Motormouth]

You want one of the 8372 variants. Probably 8372A. 8375 is only for very late model (Rev. A500 boards (and A600, etc.), unless you're using a Megachip adapter or something like that. Look up the Wikipedia article on Agnus, there's a couple other good resources out there.

+1

on the 6a and 8a motherboards ntsc or pal is control by a jumper pad.  Things get a liitle screwy on rev 5 and older.

I also suggest you read a chip ram upgrade and a motherboard ram upgrade guides before you do anything.  These can be found on aminet.

The chip ram upgrade is really easy on  a rev 6a, but you need to be more careful with the motherboard ram upgrade.  You may want to take psxphill's suggestion and get an a501 or clone, just be careful about battery damage.