Installation of racks on engine hood

It all depends on the type of rack you bought and the manufacturer of the Speedster you have.  Post some pictures. 

Hi it's a lietz style engine rack bought vehicle from vintage auto from California the racks came with 4 bolts and nuts can't figure out how to put it together 

Are the bolts long enough to go through the grill , leaving 2" or so of space above the grill and through the fiberglass rain shield (hopefully you still have it there?)  If there isn't a shoulder on those bolts - I'd put a stainless  nut and steel fender washer above the rain shield and same on engine side of it (I'd use a Nylock SS nut there as it will vibrate. 

I installed an AMCO rack on mine - the original chrome bolts weren't long enough.  I used SS threaded rod and cut to length.  I used a SS acorn cap nut on rack.  I then used chrome sink vanity tubing to cover the threaded rod and then did the fender washers recommended above.

@Dado

This is a Lietz luggage rack used on Porsche 356...

This is the luggage rack option available from Vintage Speedster (Kirk Duncan)..

1. The luggage rack is attached to the engine lid via bolts long enough to pass through the luggage rack and through the rain tray on underside of engine lid. Rest luggage rack on lid to mark where to drill holes for attachment bolts. Spacers are required to keep the Lietz luggage rack 1/2" or so above the grill on the engine lid. VS luggage rack does not need spacers.

2. Recommend using fender washers (wide flat washers) to distribute the weight of the rack and luggage. On top of engine lid, place fender washers between bolt spacer and lid...

3. Underneath lid (rain tray) place fender washer between rain tray (fiberglass) and nut. Recommend using 'nylock' nuts.

4. Careful not to over tighten nuts in order to prevent cracking fiberglass rain tray.

Hope you find this info useful.

On other models of replicas a metal cast iron big D that fits inside the lid, under the grill is bolted in and is used as a strengthening device to give the top more ability to carry the weigh. and the rack screws into it.  I don't have a pict at the moment.