In this case, my final instance specification looks like:

inst, err := compute.NewInstance(ctx, "mr. webbie", &compute.InstanceArgs{
			BootDisk: &compute.InstanceBootDiskArgs{
				InitializeParams: &compute.InstanceBootDiskInitializeParamsArgs{
					Image: pulumi.String("debian-cloud/debian-10-buster"),
					Size:  <http://pulumi.Int|pulumi.Int>(30),
				},
			},
			MachineType: pulumi.String("f1-micro"),
			Name:        pulumi.String("webbie"),
			NetworkInterfaces: &compute.InstanceNetworkInterfaceArray{
				&compute.InstanceNetworkInterfaceArgs{
					Network: pulumi.String("default"),
				},
			},
			ServiceAccount: compute.InstanceServiceAccountArgs{
				Email: pulumi.String("<mailto:1038906272696-compute@developer.gserviceaccount.com|1038906272696-compute@developer.gserviceaccount.com>"),
				Scopes: pulumi.StringArray{
					pulumi.String("<https://www.googleapis.com/auth/devstorage.read_only>"),
					pulumi.String("<https://www.googleapis.com/auth/logging.write>"),
					pulumi.String("<https://www.googleapis.com/auth/service.management.readonly>"),
					pulumi.String("<https://www.googleapis.com/auth/servicecontrol>"),
					pulumi.String("<https://www.googleapis.com/auth/trace.append>"),
					pulumi.String("<https://www.googleapis.com/auth/monitoring.write>"),
				},
			},
			Project: pulumi.String("webbie-295322"),
			Zone:    pulumi.String("us-west1-a"),
			Tags: pulumi.StringArray{
				pulumi.String("https-server"),
				pulumi.String("http-server"),
			},
		},
			pulumi.Import(pulumi.ID("1214816920423977412")),
		)