My first attempt was brute force, unremarkable, found the 474 after processing 95% of the combinations and took just under 8 hours to run.

My second finds the 474 in 0.15 seconds.

P:\test>499358-2
460 : [ alabama sangrita radiator amalgam rutabaga camellia lasagna ma
+scagni tacomayo marzipan ]
472 : [ alabama sangrita radiator amalgam rutabaga azalia lasagna masc
+agni tacomayo marzipan ]
474 : [ alabama sangrita radiator amalgam rutabaga azalia lasagna masc
+agni tacomayo taiglach ]
Elapsed: 0.015 seconds.
[download]

See comments for the strategy used.

#! perl -slw
use strict;
use Time::HiRes qw[ time ];

my $start = time;

my @lookup = map{ ($_+1) * $_ /2 } 0 .. 80;
sub calcScore {
    my( %chars, $score );
    $chars{ $_ }++ for map{ split'' } @{ $_[0] };
    $score += $lookup[ $_ ] for values %chars;
    return $score;
}

my @cats = map{ [ split ' ' ] } <DATA>;
close DATA;

## Sort the words in each category by their individual scores (descend
+ing)
my %wordScores;
@{ $cats[ $_ ] } = sort{
    ( $wordScores{ $b } ||= calcScore [$b] )
    <=>
    ( $wordScores{ $a } ||= calcScore [$a] )
} @{ $cats[ $_ ] } for 0 .. $#cats;

## form our guess from the highest scoring words in each category
my @guess = map{ $cats[ $_ ][ 0 ] } 0 .. $#cats;
my $best = calcScore \@guess;

## Loop over the categories swaping the other words in that cateory 
## for the guessed word. If we get a better score, start again.
LOOP:
for my $iCat ( 0 .. $#cats ) {
    my $cat = $cats[ $iCat ];
    for my $iWord ( 1 .. $#$cat ) {
        my $test = calcScore [ 
            @guess[ 0 .. $iCat -1 ], 
            $cat->[ $iWord ], 
            @guess[ $iCat+1 .. $#guess ] 
        ];
        if( $test > $best ) {
            $best = $test;
            $guess[ $iCat ] = $cat->[ $iWord ];
            print "$best : [ @guess ]";
            redo LOOP;
        }
    }
}
printf "Elapsed: %.3f seconds.\n", time - $start;

__DATA__
alabama arkansas alaska delaware hawaii indiana kansas montana delawar
+e
sazerac sangrita
radiator gastank engine heater fender wheel detent battery clutch mirr
+or window
alloy amalgam vanadium copper steel
rutabaga limabean cress carrot sorrel squash cabbage pepper lettuce be
+et leek celery endive rhubarb parsnip pumpkin
azalia camellia dahlia gardenia gentian vervain canna hepatica bluebel
+l anemone oleander
lasagna macaroni pastina gnocchi tortelli alfabeto
mascagni britten menotti
unamas tacotime pizzahut tacobell panago tacomayo edojapan hardees
caramel marzipan taiglach taffy brittle fondant toffee dragee
[download]